Ask MetaFilter questions tagged with math
http://ask.metafilter.com/tags/math
Questions tagged with 'math' at Ask MetaFilter.Mon, 25 Apr 2016 13:49:19 -0800Mon, 25 Apr 2016 13:49:19 -0800en-ushttp://blogs.law.harvard.edu/tech/rss60Counting 101 (and beyond)
http://ask.metafilter.com/294967/Counting%2D101%2Dand%2Dbeyond
Our three year old LOVES to say his letters and numbers. When he gets to Z, he triumphantly (and accurately) announces "and that's all the letters!" When he gets to 100 he proudly informs us, "that's all the numbers!" I've tried to tell him about 101, 102, etc., but he does not believe me. He would believe it if a YouTube video or app told him so. Any suggestions? (Yep, I know this is not a big deal. I just like watching the light bulb go on when he realizes just how big the world is.)tag:ask.metafilter.com,2016:site.294967Mon, 25 Apr 2016 13:49:19 -0800slmorriScience for 6-year-olds?
http://ask.metafilter.com/294482/Science%2Dfor%2D6%2Dyear%2Dolds
Can you recommend either a good homeschooling science curriculum for K-1st grade, and/or an experiments that work well for 6 year olds, and/or advice on devising an ongoing science course for kids that age? My son's science program at his kindergarten leaves a lot to be desired, and I don't think it's going to get better in the upper grades. I and a couple of other parents would like to supplement with essentially our own after-school science and math curriculum, at home. (We would do this together, taking turns hosting.)<br>
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Google gives me an overwhelming number of options for purchasing books. It also gives me a gazillion hits for "science experiments for kindergartners." I'm also hampered by the fact that my own science and math education was underwhelming, and I have no way of evaluating what's good or not. <br>
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I have a vague idea that they should be learning, at this stage: Simple biology (growing plants, finding out what happens if plants don't get enough light and water, bird-watching); simple chemistry experiments; simple mechanics/physics like building things and seeing how much weight different designs can hold.<br>
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But I have no idea where to start. Any suggestions?tag:ask.metafilter.com,2016:site.294482Tue, 12 Apr 2016 14:33:03 -0800piptiMath problem alert: NCAA Magic or Unsurprising?
http://ask.metafilter.com/294230/Math%2Dproblem%2Dalert%2DNCAA%2DMagic%2Dor%2DUnsurprising
We had a NCAA March Madness contest at work, where about 40 of us all filled out brackets on ESPN's site. One of us - the winner of our group - did very well and ended up ranked 6000th out of all 13 million ESPN brackets - top .05%. My question is, was this really statistically unlikely or, given that there were 40 of us, is it unsurprising one of us did that well (e.g., the birthday problem)? What mathematical tools would one use evaluate this question? Thanks!tag:ask.metafilter.com,2016:site.294230Wed, 06 Apr 2016 12:04:40 -0800slideHelp our elementary school get gender balance in gifted math and science
http://ask.metafilter.com/293854/Help%2Dour%2Delementary%2Dschool%2Dget%2Dgender%2Dbalance%2Din%2Dgifted%2Dmath%2Dand%2Dscience
Today I had to have the uncomfortable discussion with my 5th grade daughter about "why there aren't more girls on the Science Bowl team." Apparently, there are 5 girls out of 16 competitively awarded spots. A couple of years ago, we had the exact same discussion about TAG math-- she wanted to drop out because she was the only girl in her group. Back then, I talked to the school administration, and they moved her to a different TAG math group with a few more girls in it. And I have been fighting the "no, you're not bad at math. Girls are not bad at math" fight ever since. I am now pretty angry at myself for not pushing the issue of gender disparity then.<br>
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So today? Today I am angry enough to call up the school and ask them point blank to explain the gender imbalance in their science and math performance/opportunities for boys and girls. But rather than going in full of rage, I want to engage with the school on how to increase girls' engagement in math and science. I know for a fact that there are other bright, competent girls interested in math and science in her class. Statistically speaking, the TAG Math and Science Teams should be about 50-50 girls and boys. The fact that my 10 year old daughter now thinks that boys are better at math and science (and now is less enthusiastic about math as a result) is <em><a href="http://www.nytimes.com/2015/02/07/upshot/how-elementary-school-teachers-biases-can-discourage-girls-from-math-and-science.html">damaging her future educational and employment opportunities</a></em>. <br>
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So. Teachers and STEM advocates of MeFi: tell me how to do this productively. I want to go in with research-based suggestions on bringing more girls into math and science programs, but I don't know where to start.<br>
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Here's what I think:<br>
- in general, her school is great on science! That's one reason she loves it and is good at it. But for my bright science-loving girl, the existence of advanced science and math opportunities is turning out to be a net negative rather than net positive, because the message she's taking home from it is "girls don't do math and science as well as boys."<br>
- I suspect that part of the imbalance is caused by how the advanced math and science groups are vetted (is basing science teams on written tests appropriate in elementary school? That seems like it would miss a lot of smart science-interested kids with different Gardner multiple intelligences). <br>
- If there isn't any give about the TAG and science teams, could the school offer other types of science and math enrichment that they work harder to balance across gender (race, socioeconomic diversity, learning styles, etc)? Any suggestions for how to set up something like that? Ideas on productive parent involvement, if that would help it happen?<br>
- What types of science and math activities are particularly engaging to a wider range of students? (The science team seems to be fairly "Jeopardy for kids, with science"-- I wonder whether projects or clubs would draw-and permit- more girls?)<br>
- What else should I know? What should I be asking of the school administration, the teachers, and other parents? <br>
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We do a lot of science and math exploration at home, so it's less that I'm worried that she won't get math and science if she doesn't get it at school. (I suspect that's part of why she's been persistent enough to keep at it in school, even as one of the few girls.) It's that school is making it <em>harder</em> to keep her engaged in math and science, rather than easier.tag:ask.metafilter.com,2016:site.293854Mon, 28 Mar 2016 15:23:20 -0800instamaticI'm looking for a daily or weekly customization math problems
http://ask.metafilter.com/293724/Im%2Dlooking%2Dfor%2Da%2Ddaily%2Dor%2Dweekly%2Dcustomization%2Dmath%2Dproblems
I'd like to receive daily or weekly emails with a math problem. Do you know of a service like this that exists? It would be preferable if I could tweak the settings to include only problems from certain disciplines (eg Calculus). It doesn't have to be delivered via email, although that would be preferred. Alternatively, if you know of a good site with a well designed user interface that can provide these problems, (and solutions), I could set my own daily/weekly reminders.tag:ask.metafilter.com,2016:site.293724Fri, 25 Mar 2016 10:32:32 -0800czytmStatistical framing of the engineering and extremism article
http://ask.metafilter.com/293713/Statistical%2Dframing%2Dof%2Dthe%2Dengineering%2Dand%2Dextremism%2Darticle
Reading <a href="http://www.metafilter.com/158088/Does-Engineering-Education-Breed-Terrorists">this </a> article on the blue got me thinking about conditional probabilities, prediction and causality. I came up with an analytical framing of what I think the article is saying and would be grateful if stats/social science Mefites could tell me if it seems accurate or else set me right. Reading this article on the blue got me thinking about conditional probability in a simple discrete 2x2 case. <br>
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Suppose there are two discrete random variables in a population of individuals, A and B. According to conditional probability, P(A,B)=P(A|B).P(B)=P(B|A).P(A). <br>
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If A and B are statistically independent then P(A|B)=P(A) and P(B|A)=P(B). <br>
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Suppose A and B are not independent. Suppose P(A|B)=k.P(A), k>1 But since<br>
P(A,B)=P(A|B).P(B)=P(B|A).P(A) then this implies that k.P(A).P(B) =P(B|A).P(A). Cancelling the P(A)s gives P(B|A)=k.P(B) with k>1. <br>
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So I was thinking about this <a href="http://www.metafilter.com/158088/Does-Engineering-Education-Breed-Terrorists">article</a> about engineers and extremist. <br>
I tried to put the article in the framing above. The way I see it, it could be framed for statistical purposes that the world’s population can be partitioned separately by two random variables. Engineer or not-engineer, and extremist or not extremist.<br>
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The article notes evidence that suggests that P(engineer|extremist)>P(engineer). I.e. engineers are more prevalent among extremists than they are among the general population. The article then considers explanations of the fact.<br>
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However, as far as I can see the algebra above suggests that if the above is true, it IMPLIES that<br>
P(extremist|engineer)>P(extremist), just by the way the 2x2 discrete partitioning and conditional probability works. <br>
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I find this a little shocking. As I was reading the article I was sort of turning my nose up at some of the explanations, and the title, which to me sounded a bit like evidence for P(engineer|extremist)>P(engineer), rather than P(extremist|engineer)>P(extremist). Before I went through the algebra, I assumed it would be possible that P(engineer|extremist)>P(engineer) could be consistent with P(extremist|engineer)=P(extremist), but from the algebra above it appears that this is not the case. Possibly in my original thoughts I muddled prediction and causality.<br>
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What I would like to know is what implications does the 2x2 discrete partition case have for the example, if it turned out to indeed be the case that P(engineer|extremist)>P(engineer). Does it mean, for example, that as an estimator, in this case rather than looking at a sample of extremists and counting the proportion of engineers among them, we could in principle look at a sample of engineers and count the number of extremists? [Aside from the practical problem that we would need to sample a huge number of engineers to sample any extremists at all.] <br>
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Please note: I am aware that statistical dependence is not the same as causality, and that there is a separate “causal” calculus in the statistics/probability literature by Judea Pearl and others, which among other things respects the fact that cause can be unidirectional whereas statistical information flows both ways (i.e. we can predict and retrodict things which both may or not be causally related). I am aware that there is a special P(A|do(B=b)) notation to denote causality. (I have been reading part IV of Cosma Shalizi’s <a href="http://www.stat.cmu.edu/~cshalizi/ADAfaEPoV/ADAfaEPoV.pdf">book</a> here )) As I understand it, the special causal “do” refers to a manipulated distribution. Crucially, the manipulated distribution may not be identifiable from observations which you cannot control by experiment. Also note I am interested in the statistical/social science framing of the debate here, not trying to make some kind of oblique point about extremism.<br>
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Secondly, I would like to know whether this is a reasonable statistical/social science framing of the article:<br>
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<em>There is evidence P(engineer|extremist)>P(engineer). I.e. there is a selection effect that causes there to be a higher proportion of engineers among extremists than there are engineers among the population as a whole. Could the reason for this be that engineers are more likely to be extremists, i.e there is some statistical causality running from engineers to extremism, because of certain psychological traits of engineers?</em> <br>
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This is where the psychological explanations are brought in. (In causality notation I think exploring this psychological argument would look like an enquiry as to whether P(extremist|do(Engineer))>P(extremist|do(Not engineer)). Others in comments note that when it comes to specifically terrorist extremists, the selection effect possibly explains itself, since presumably engineers are a large part of the few those with skills to carry them out. So inference to the simplest explanation would suggest that the causal explanation that flips the conditioning for the original observed selection effect and imposes a casual“do” is not required. <br>
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Do you think I am on the right lines with this analytical framing? I’m sure you will let me know if I’m far off base here. Many thanks.tag:ask.metafilter.com,2016:site.293713Fri, 25 Mar 2016 07:01:10 -0800mister_kaupungisterCheck My Math Please!
http://ask.metafilter.com/293173/Check%2DMy%2DMath%2DPlease
I need this for a work report, so I want to make sure I am doing this right. Could someone please verify or correct me, please?
I have two percentages and I need to figure out what percentage of change has taken place.
64.24% has changed to 74.24%
So, I think I need to do this: 74.24 - 64.24 \ 64.24 = 15.6% improvement <strong>or</strong>
74.24 - 64.24 \ 74.24 = 13.5% decreasetag:ask.metafilter.com,2016:site.293173Fri, 11 Mar 2016 08:55:13 -0800LilithSilverExcel arithmetic glitch explanation
http://ask.metafilter.com/292684/Excel%2Darithmetic%2Dglitch%2Dexplanation
This isn't getting in the way of anything practical, but it's niggling that I don't understand the technicalities. An accounting spreasheet I've used daily for years has thrown up an Excel glitch... from some googling it seems to be something related to the way floating-point arithmetic is handled as per <a href="https://support.microsoft.com/en-gb/kb/78113">this article.</a><br>
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The specific example is:<br>
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<em>=34606.95-31740.06-2866.89</em> calculates to <em>-4.09272615797818E-12</em><br>
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but a re-ordering<br>
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<em>=34606.95-2866.89-31740.06</em> calculates, as it should, to <em>0</em><br>
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This isn't remotely a practical problem, but can you please explain (to someone keen but with no formal cs background) the specifics of what's going on here?tag:ask.metafilter.com,2016:site.292684Mon, 29 Feb 2016 04:23:06 -0800protorpHelp me develop complicated spreadsheet
http://ask.metafilter.com/292436/Help%2Dme%2Ddevelop%2Dcomplicated%2Dspreadsheet
Note: NOT Homework. Real world application here.
I have to come up with a spreadsheet based on a formula that allocates dollars to people based upon role and participation. I'm good at Excel but this one is boggling my mind. Details and example inside I need to come up with a spreadsheet for profit sharing among a team. The team has several people, and many fill multiple roles. So to use an example of a garage sale:<br>
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The garage sale happens weekly, so four times a month. Different people staff the garage sale.<br>
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There are multiple roles: Some people set-up the sale, others are cashiers, and then some do price research. Then there's the managers who oversee it.<br>
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The payout is by role. So of the total Garage Sale income IN THE MONTH (not per sale), the manager(s) get 15%, the set-up people get 20%, the cashiers get 35%, and the price researchers get 30%.<br>
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Some people work multiple roles (a cashier may also do set-up, etc). And some people may work all 4 garage sales that month, some just 1. <br>
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So the formula per role is:<br>
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Managers: (Total Income * .15) = Manager Role's total amount to divide among the managers. <br>
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But then if one manager worked all 4 shows, another manager assisted with 2 shows, and a third manager worked just 1. So there were 7 manager "shifts" total. That breaks down to about 14% per "shift". <br>
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So the first manager would get 57%, the second 29%, and the third 14%.<br>
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But the next month perhaps only 1 manager would work each show, so 4 shifts total, and that manager would get 100% of the manager's 15% take<br>
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Finally complicating things, the manager could also work set-up or as a cashier. So the manager would get their portion of the 15%, but also a portion of each of the other roles.<br>
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Then each person only gets paid if their total amount is over $50. If it's under $50 the amount rolls over to the next month until they get $50. So I need to store a running total of how much they earned, <em>and</em> how much was paid out to them.<br>
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I figure there must be a way to do this in a spreadsheet, but I'm at a loss on how to store this data. I'd like the spreadsheet to store a year's worth of data. <br>
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I am imaginging rows for each person, columns for each month, but then...columns for each role as well? And how do we count how many shows were done in that month, and store that month's specific income?<br>
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Anyone able to suss this out?tag:ask.metafilter.com,2016:site.292436Tue, 23 Feb 2016 07:06:43 -0800arniecLet's play: math problems with a comm major!
http://ask.metafilter.com/292182/Lets%2Dplay%2Dmath%2Dproblems%2Dwith%2Da%2Dcomm%2Dmajor
I'm having trouble wrapping my head around a math equation I need to create, possibly because the data I have to cook something up with is less than ideal and only good for faking a preliminary number. Maybe you can help... I have a pool of sales leads that is being split into two categories. The leads from category A represent 40% of the number of leads in the pool, but generate 70% of our income. The leads from category B represent 60% of the leads, but just 30% of the income. Assuming the average close rate of these sales leads was X%, how do I adjust the anticipated success rates for the two divided pools?<br>
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Trying to come up with an algebraic equation for this is making me want to get onto a train headed to Cleveland at 100 mph, directly in the path of a train coming from Cleveland at 60 mph.tag:ask.metafilter.com,2016:site.292182Tue, 16 Feb 2016 12:13:03 -0800DirtyOldTownHelp me figure out this number-of-combinations problem
http://ask.metafilter.com/292051/Help%2Dme%2Dfigure%2Dout%2Dthis%2Dnumber%2Dof%2Dcombinations%2Dproblem
Supposing you have a set of N number of questions to choose from for creating a test. Your test must have a minimum of 1 question but can have all N. How many unique tests could you create?
Am I correct to assume the formula is 64! (factorial)?
64 x 63 x 62 x 61...tag:ask.metafilter.com,2016:site.292051Sat, 13 Feb 2016 01:11:41 -0800postergeistHow do I sort folks into groups based on their preferences?
http://ask.metafilter.com/291896/How%2Ddo%2DI%2Dsort%2Dfolks%2Dinto%2Dgroups%2Dbased%2Don%2Dtheir%2Dpreferences
What kind of algorithm can I use to create optimal group assignments for people, given each person's ranked preferences and limitations on group size? I'm having a hard time coming up with good search terms for this kind of thing.
If an example helps: I have 115 people and 16 groups. Each person needs to go in a group. Each person will submit a list of their preferred groups in their preferred order. Some groups can hold up to 10 people, while others can hold up to 5. For the purposes of this exercise, let's pretend that no one cares who else is in their group with them.tag:ask.metafilter.com,2016:site.291896Tue, 09 Feb 2016 14:59:42 -0800lizzicideLooking for math and science 'jokes' to slip into a D&D adventure!
http://ask.metafilter.com/291816/Looking%2Dfor%2Dmath%2Dand%2Dscience%2Djokes%2Dto%2Dslip%2Dinto%2Da%2DDandD%2Dadventure
I've got the chance to run a fun, whimsical sort of D&D adventure for a friend of mine. Yay! She's a bit of a science/math geek, and very fond of The Phantom Tollbooth by Norton Juster. So I was trying to think of fun, whimsical science and math jokes and references I could slip in to a sort of 'journey with sights along the way' in the style of TPT. For example, I thought at some point she could explore a fractal dungeon, where the main design of a center room is repeated into tinier and tinier configurations around the edges, eventually too small to enter. And being a Discworld fan, I thought the mysterious monster “The Shadowing Lemma” (“that only exists in two dimensions, and eats mathematicians”) could make an appearance somewhere. (I'd use a Shadow Mastiff as the D&D equivalent monster.) <br>
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What are some other fun and quirky and interesting math/science concepts that could make an appearance in a fantasy world? She's played the game plenty, and likes the exploration/fantasy/storytelling/puzzle-solving aspect of the game more than raw combat and power. We're playing 3.5 D&D if it matters, and her character is level 12. Thank you in advance for any suggestions! :)tag:ask.metafilter.com,2016:site.291816Sun, 07 Feb 2016 11:12:46 -0800The otter ladyWhat sort of genius do I need to hire, and where can I find them?
http://ask.metafilter.com/291616/What%2Dsort%2Dof%2Dgenius%2Ddo%2DI%2Dneed%2Dto%2Dhire%2Dand%2Dwhere%2Dcan%2DI%2Dfind%2Dthem
I am in the process of trying to create a complex pricing calculator for internal use in our business. I have most of the data, however I am hoping to engage someone on a freelance basis to help me complete the data set, as well as give some expanded detail on how this data (pricing) can change geographically. What specific professions should I be engaging, and where can I find them? <em>More information below the fold.</em> Assume that we sell a product that is highly customisable. There could be hundreds, if not thousands, of different combinations and variations. The closest thing that comes close to what we want to do would be the Getty Images Pricing Calculator (To view it, go to getty images, click on an image, and then get the calculator open to see the options).<br>
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Now assume that I have general data points of pricing for the territory that I am in, and a few other major territories. I might not have all the data, but I might have the lowest price, the highest price and the medium price. I might also have some other generalised ideas on how the other prices could be calculated (i.e, on a percentage basis), and how certain stacking of options could lead to discounts. Either way, the general prices have been set, and this process would be like 'tweening' (Think of Flash Animating - You set a beginning state, and end state, and then Flash generates the in-between states)<br>
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This tool that we want to develop is really more for estimating purposes rather than looking at hard costs etc. It would not be public facing, and it's really just a way that we can hopefully speed up our quoting process.<br>
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Off the top of my head, I thought I would need to engage a Mathematician for the core function above, and perhaps some sort of economist, in terms of trying to apply those pricing estimates to different global regions. That said, both of these fields are pretty much greek to me, and I'm not even sure these would be the appropriate parties, and if they are, where and how to find them, apart from Metafilter jobs for example.<br>
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If this makes even a bit of a sense to anyone else other than me, please chime in or memail me! Thank you :)tag:ask.metafilter.com,2016:site.291616Mon, 01 Feb 2016 23:52:34 -0800sxtrumpetoLooking for sites or books like Cosma Shalizi's notebooks
http://ask.metafilter.com/291538/Looking%2Dfor%2Dsites%2Dor%2Dbooks%2Dlike%2DCosma%2DShalizis%2Dnotebooks
I really like the short explanations and exhaustive trove of links found in Cosma Shalizi's notebooks. Are there any other similar sites or books out there? I'm looking for sites or books where a high level or intermediate level of description is given about a topic and then a large number of primary or secondary sources is provided for the reader. My interests lie in math, computer science, and programming, but any such sites are welcome.<br>
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Yes, I know Wikipedia does this to some extent, but looking for stuff that is more curated and personal.<br>
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Thanks!tag:ask.metafilter.com,2016:site.291538Sat, 30 Jan 2016 16:26:24 -0800reenumI need some new ideas for scoring non-competitive fencing nights
http://ask.metafilter.com/291412/I%2Dneed%2Dsome%2Dnew%2Dideas%2Dfor%2Dscoring%2Dnon%2Dcompetitive%2Dfencing%2Dnights
I am part of a fencing club that includes a wide range of fencers, some inexperienced, some very competitive, some young teens, some over 60 and lots in between.
I have started organizing a monthly "goofball" tournament to bring out the members and to have chances to win prizes and it is going very well.
The aim, however, is not to ensure the top fencer always wins -- we have plenty of tournaments for that. What I want is to encourage maximum participation for every fencer to get on the piste and be motivated to fence a lot, and have fun. Here is my summary of goofy games nights so far<br>
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<strong>nights 1 & 2</strong> The first two had simple rules: over the course of the night, record all your scores, and whoever tallies the most at the end wins. You could win by having the most bouts or lots of wins. the winner the first time got a mini jackolantern gourd named "the gourd of infamy" The second time crowd won medals I made from bananas called "the fearsome banana of hyperbole" and bragging rights until the next event. <br>
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<strong>Night 3</strong> Steal your name night is when you are re-named by any opponent that beats you. <em>(This is a long standing event for the club. I was known as Target for many months following one such night.)</em><br>
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<strong>Night 4</strong> The last one had bunny-ear hair bands and garlands and was billed as "meadowland bunny cull battle". Players put bunny ears headbands on their helmets. You had to lop off the ears of your opponent while in the bout. Over the course of the night these garland headdresses were awarded for various things -- one to the fencer who won a game of Musketeers (three fencers lined up per side must try to knock the ears off those on the other side without crossing a line), one to someone who managed to ingeniously lodge a garland and bunny ear combo into her helmet so it was impossible to remove through he whole night, and one to a beginner who had an excellent night (maybe due to the fact that his opponents were busy with all their ear attach leaps and fleches).<br>
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I learned from the bunny ears event that some of the younger fencers were a bit disappointed if it wasn't clear what they should try to do to win from the beginning. So that is ok sometimes, but maybe not every time.<br>
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<strong>Idea 5 </strong> My next plan is to have jars where you have to guess the number of red jelly beans, and then try to get the points that match. At the end, you reveal the numbers and winners claim their jar of jelly beans if they had up to or equal that number of points. the jars can be made to bell curve, thus giving chances to a wide variety of fencers. Perhaos they could also be number+other attribute (number of bouts, number of opponents, number of points in first six bouts, number of points overall)<br>
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<strong><br>
idea 6</strong> My son has this crazy averaging idea to try to get people to try harder against difficult opponents .. you tally all your points, but through the night if you beat someone, you get 1+ point for every bout they win, and -1 point for every bout they lose. Thus you really want to defeat opponents that are tougher than you (he thinks).<br>
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<strong>idea 7</strong> I also thought of <a href="http://www.metafilter.com/155168/12-Games-For-Christmas">this post</a> and the average Christmas card game, modified so that the person who has the average number of points wins (?). Perhaps with three points of awarding.<br>
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<strong>General thoughts</strong><br>
Everyone at the club has a great sense of humour and is game to try things to get members out fencing as much as possible -- especially to encourage the teens to get lots of exercise. they proudly pose with their prizes for photos and some parents say that games night means their kid demands to attend no matter what. <br>
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Ideally there is also a change to develop skills even if the game is goofy -- i.e. keeping distance with the bunny ears.<br>
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What I particularly struggle with is finding ways to score things that is not formal tournament scoring. At the club we usually fence to 5 points, but also sometimes to 15. it is sometimes hard to fence everyone in one night for laddering. We fence for about 1 h 45 min outside set up and clean up.<br>
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Any suggestions of goofy games from other sports I could modify?<br>
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Any fencing clubs have games you have used that have been popular with a range of fencers?tag:ask.metafilter.com,2016:site.291412Wed, 27 Jan 2016 15:20:42 -0800chappsChristmas math
http://ask.metafilter.com/289901/Christmas%2Dmath
Oh hai. <a href="http://ask.metafilter.com/289186/Another-gift-question-game-edition">This was me</a>. Awesome responses. Now I need some help with cryptograms. I decided to get my husband a cryptogram puzzle box and put the info for the game in that. The box has a five-letter solve (so you have to put the five letters in the right combo to open the box). I'd like to do a scavenger hunt where each clue gives him a letter and leads to the next one. I'd like one clue to be a math puzzle whose answer is a letter and another that's a coding puzzle whose answer is a letter. <br>
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Specifics:<br>
-- His math and programming levels are extremely high and he knows most programming languages, but specifically Ruby. <br>
-- I don't care what the letters are that he solves for.<br>
-- Answers to these puzzles shouldn't be easily googable.<br>
-- Assume my level of math and programming is rudimentary at best.<br>
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Any ideas? I think this could elevate this gift to pretty sweet levels!tag:ask.metafilter.com,2015:site.289901Sat, 19 Dec 2015 19:04:43 -0800mrfuga0Help Me GRE Math Study During My Bus Commute
http://ask.metafilter.com/289692/Help%2DMe%2DGRE%2DMath%2DStudy%2DDuring%2DMy%2DBus%2DCommute
I'm gearing up to study for the GRE, but I haven't done math in...10 years? I usually read on my Kindle on the 30 minute bus ride to and from work, so I was hoping that I could instead start using this time for math studies! The bus is often standing room only so I was hoping for some recommendations for math-focused apps or GRE ebooks I could use on a Kindle or iPhone that would help me get back in the groove. I've started watching some of the Kahn Academy SAT videos while I'm at home, but I don't have enough data on my phone plan to watch videos for an hour each day on the bus.<br>
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Step-by-step instructions for figuring out the answers are pretty key, as I don't really remember anything from high school. I was never particularly good at math anyway. Ideally, I'd love to start using some kind of interactive type learning app that could help me keep track of what skills I've mastered and what still needs work. I have at least 6 months to study.<br>
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Any other GRE study advice is also welcome!tag:ask.metafilter.com,2015:site.289692Mon, 14 Dec 2015 16:21:39 -0800forkisbetterNext step beyond Lego?
http://ask.metafilter.com/289269/Next%2Dstep%2Dbeyond%2DLego
My son has mostly outgrown Lego but still loves building things from instructions. Challenging things. What are some building kits I could get for him? He's 13, in eighth grade. Loves math and engineering stuff. Loves building things. <br>
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<strong>He likes:</strong><br>
Architecture (he designs cities in City Skylines)<br>
Minecraft<br>
K*Nex<br>
Lego<br>
Putting together Ikea furniture. Seriously, when he was five he started helping me put together some Pax closet organizers and I eventually left him alone to complete the job. <br>
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<strong>He's not really into:</strong><br>
Robotics (he has Minestorms already)<br>
Programming <br>
Electronics<br>
Lego Tecnic Sets <br>
Messy things like glue. He has texture issues. <br>
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I'd like to get him some sort of kit where he could build something complex. Think Erector Set but more... real. If I could afford to get him a 3D printer kit I would, but I can't. But something along those lines. A complex kit that would take him several hours (or days) to build from instructions using basic tools. <br>
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This should be something physical, not virtual. Something mechanical. <br>
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Parts should be ready made. Nothing that he'd have to cut or saw. Nothing that could be easily screwed up. <br>
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Not Arduino. I asked him about that and he really wasn't into it. It's ok if the kit has some electronics but it shouldn't be just an electronics kit. <br>
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Not Minestorms or Lego Technic. No more K*Nex. No more ball machine structures. Not a robot. He has a bike already. <br>
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Ideally, he would build something that he could then use or display for a long time, or take it apart and build it again. <br>
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Target price maybe $100? I could go higher for the right thing.tag:ask.metafilter.com,2015:site.289269Fri, 04 Dec 2015 07:51:21 -0800bondcliffMath Educators: Is there a name for this?
http://ask.metafilter.com/289174/Math%2DEducators%2DIs%2Dthere%2Da%2Dname%2Dfor%2Dthis
My eight year old has devised his own way of doing subtraction with re-grouping and it makes me wonder if this is a known "wrong" way of doing things that is part of the "normal" learning process, such as the way that many children write letters backwards and it doesn't necessarily mean anything, or if it is more unusual. For what it's worth, his teacher, who has a masters degree in mathematics herself, has not seen a child do things this way before. If you ask my son what 3 minus 5 is, he will tell you 2. His method for solving problems that involve regrouping, such as 23 minus 15, is not to turn the problem into 13 minus 5, but rather to turn it into 10 minus 2. He subtracts the lower number from the higher one in each column, regardless of which one is on top or bottom, then, if the number is a negative number (although he doesn't refer to it that way), he borrows 10 and subtracts his number from it. He can do and understands doing subtraction with regrouping the "normal" way, but devised this way for himself and this is his preferred way of doing it. <br>
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His math education comes mainly from Singapore Math and Khan Academy. My math education came mainly from "this is how you do this, memorize it, and do it", so the idea that someone might do basic subtraction their own way was a bit of a surprise to me. Is it actually surprising to anyone who teaches elementary mathematics? Does it possibly indicate anything about my son in terms of learning challenges he may have?<br>
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I hope this doesn't sound ungracious, but I'm looking for answers from people who know something about how children acquire math skills, rather than anecdotes from people about how they learned math themselves.tag:ask.metafilter.com,2015:site.289174Tue, 01 Dec 2015 19:35:19 -0800toodlesDo I need to crash a high school stats class?
http://ask.metafilter.com/288375/Do%2DI%2Dneed%2Dto%2Dcrash%2Da%2Dhigh%2Dschool%2Dstats%2Dclass
Where do English majors go to learn key principles behind<strong> deriving mathematically sound meaning from data</strong>? I worked for years as a digital editor. Now I'm a "content strategist," which means I'm responsible for proving my new strategy increases reader engagement via different metrics like UVs, shares, attention time, average story finish rate, etc.
I'm very familiar with platforms like Google Analytics and Chartbeat. But I want to learn how to see patterns in them there numbers, and I NEED to make sure my insights are mathematically accurate. How can I most efficiently do that without getting a brain transplant?
(Example below.) For a current client, I'm comparing how Oct Stories A performed compared to October Stories B across 5 different metrics. (The data comes from a proprietary analytics tool.)<br>
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All stories were distributed during the same time period on the same platform (Outbrain). It took me forever to figure out that I had to calculate the "percentage difference" instead of "pecentage change between the two groups, and that i have to ensure the ratio of both groups is roughly even. (I'm comparing 9 stories against 11.)<br>
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Ratios, percentages: this stuff is not rocket science. But I'm aware I don't know what I don't know. What is the most efficient way to get schooled? A math tutor? Stats 101? Excel training? A lot of data classes focus on the platform but not the meaning behind the numbers.<br>
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Thanks!tag:ask.metafilter.com,2015:site.288375Thu, 12 Nov 2015 11:14:40 -0800jessca84Add learning disorder, subtract job
http://ask.metafilter.com/287729/Add%2Dlearning%2Ddisorder%2Dsubtract%2Djob
I have a learning disorder called <a href="https://en.wikipedia.org/wiki/Dyscalculia"></a> and as a result my math skills are somewhere around a 4th grade level. I can't turn a 3d into a 2d drawing or vice versa and I really can't count money but for going painfully slow.
Since I graduated high school I've been looking for a job that I could do where my cognitive function deficits will cause problems keeping the job. So far, lots of odd jobs and low-end jobs with nothing more solid or long term (or better paying). I've thought about going back to school but almost everything requires some kind of math or chemistry.
I like working with my hands but my difficulty with math means that doing things like welding (which I trained for) are out because I can't handle the numbers.tag:ask.metafilter.com,2015:site.287729Wed, 28 Oct 2015 20:37:25 -0800SocinusMathematical permutations
http://ask.metafilter.com/287507/Mathematical%2Dpermutations
I've gotten multiple answers to this question, so I'm coming to the good folks here for consensus!
Given an 8 character string, where each character can be one of 31 different potential values, how many different unique combinations can you create (with the supporting mathematical explanation and reasoning)? No, this isn't for homework. Ha. To clarify, of string "abcdefgh" where each variable (a,b,c,d,e,f,g,h) can be one of 31 values (lets say a symbol or alpha-numeric of some origin), and it is allowable for a=b=c=d=e=f=g=h (so QQQQQQQQ is a valid result if Q is within the 31-value allowable set) and I am not limited by Lyndon words restrictions. What is the full potential universe.<br>
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So far, I've had an argument between 8^31, or 31^8, variations of factorials (31!/8! and reverse), and the Lyndon word calculation, which would appear to incorrectly exclude AAAABBBB and BBBBAAAA from co-existing as unique value.<br>
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I have my ideas, but looking to see if my reasoning is sound.tag:ask.metafilter.com,2015:site.287507Fri, 23 Oct 2015 12:31:35 -0800richCan an exact measurement ever be statistically insignificant?
http://ask.metafilter.com/287105/Can%2Dan%2Dexact%2Dmeasurement%2Dever%2Dbe%2Dstatistically%2Dinsignificant
I am dubious of a colleague’s assertions about statistics. Say I work for the corporate office of a grocery chain. We want to monitor how often milk is on the shelves of our stores past its sell-by date. We have an annual inspection day when we send inspectors to all the stores to look at every container of milk and count up how many are still good and how many have expired. (For purposes of this hypothetical, let’s set aside the question of whether food is actually still good past its sell-by date.)<br>
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1. We’re looking at the results for a small store that had only 5 containers of milk in stock, and 2 of them were expired; thus 60% of containers were in-date. Is there any basis for saying that this finding is not statistically significant?<br>
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2. Now we want to compare the store from #1 with a larger store at which 80 out of 100 containers were in-date. Is there any reason to say that the comparison between 60% and 80% lacks statistical significance?<br>
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My recollection from long-ago statistics class is that confidence intervals and statistical significance only come into play when you’ve taken a sample from a larger population and are using it as an estimate of what is true of the whole population. My colleague is so insistent, though, that I’m doubting myself.tag:ask.metafilter.com,2015:site.287105Wed, 14 Oct 2015 14:48:47 -0800lakeroonGodel, Escher, Bach: worth it?
http://ask.metafilter.com/286930/Godel%2DEscher%2DBach%2Dworth%2Dit
Is it a waste of time for me to even attempt to read <em>Godel, Escher, Bach</em> when I don't have a very good foundational knowledge of math? <em>GEB</em> appears on practically everybody's must-read list. But these folks frequently seem to be computer science professionals who already have a lot of pre-existing understanding of recursion or other abstract mathy things. <br>
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I'm a layperson with terrible math skills but a small amount of programming experience. Will I get anything out of the project of reading <em>GEB</em>? And if so, are there supplemental readings that can help?tag:ask.metafilter.com,2015:site.286930Sat, 10 Oct 2015 05:01:00 -0800overeducated_alligator