Ask MetaFilter questions tagged with math
http://ask.metafilter.com/tags/math
Questions tagged with 'math' at Ask MetaFilter.Tue, 19 Jul 2016 07:37:54 -0800Tue, 19 Jul 2016 07:37:54 -0800en-ushttp://blogs.law.harvard.edu/tech/rss60Help with Excel formula to compare 1 column of numbers to other columns.
http://ask.metafilter.com/298334/Help%2Dwith%2DExcel%2Dformula%2Dto%2Dcompare%2D1%2Dcolumn%2Dof%2Dnumbers%2Dto%2Dother%2Dcolumns
I have an excel sheet with 4 columns of numbers. The first column is a recent donation amount. The other three columns were the prompts of donation amounts, (the Reach, the Target, and the Anchor). Is there an excel formula that can compare these four columns? I would like to use a formula to compare the donation amount to the three other columns and output results that would say the donation was, Above Reach, Equals Reach, Between R and T, Equals Target, Between T and A, Equals Anchor, and Below Anchor. Is there an easy way to do this?tag:ask.metafilter.com,2016:site.298334Tue, 19 Jul 2016 07:37:54 -0800andoatnpExcel Formula to Weight Ratings By Number of Ratings?
http://ask.metafilter.com/297820/Excel%2DFormula%2Dto%2DWeight%2DRatings%2DBy%2DNumber%2Dof%2DRatings
How do I write an Excel formula to weight a rating by the number of ratings, so that a 4 with tens of thousands of ratings weighs more than a 5 with three ratings? I have a list of books with rating and number of ratings. For example, a line of data might be, in columns A, B and C, respectively: "Firestarter, 4.8, 42573" or "Funny Anemones, 5.0, 3".<br>
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I'd like to sort these by rating, but sort them in a way where a higher number of ratings makes a rating more valuable. For example, a five-star rating from two ratings would mean a lot less than a four-star rating from a thousand ratings.<br>
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<a href="http://math.stackexchange.com/a/942965">The closest answer I could find via Google was this</a>, but the math in that answer is above my understanding, so that I don't know how to translate it into a formula.tag:ask.metafilter.com,2016:site.297820Tue, 05 Jul 2016 09:14:51 -0800WCityMikeSearching for a math learning book for children
http://ask.metafilter.com/297807/Searching%2Dfor%2Da%2Dmath%2Dlearning%2Dbook%2Dfor%2Dchildren
Sometime within the last two years, I read a positive review of a mathematics book for children of at least kindergarten age that introduced math concepts using the number line as a conceptual focus. I'd appreciate any help in trying to identify this book. The phrase "number line" may have been part of its title, however I don't think it is <em>Hopping on the Number Line</em> by Nancy Allen. I seem to recall there may have been some dynamic activity involving said number line, like breaking it or smashing it or some other colorful (but apparently not colorful enough!) imagery. I suspect there may have been an emphasis on visualization.<br>
If this doesn't ring any bells, I would also appreciate any recommendations on math learning books for young (kindergarten to early school-age) learners with a strong focus on visualizing numbers and their properties.tag:ask.metafilter.com,2016:site.297807Tue, 05 Jul 2016 03:47:53 -0800SvejkMathematical patterns
http://ask.metafilter.com/297242/Mathematical%2Dpatterns
Does this math pattern have a name? How can I find more like it? My son, 9 years old, loves math. Last year, he told me that he was thinking about math while lying in bed one night before sleep – you know, as you do!-- and this pattern had occurred to him:<br>
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n^2 + (n+n-1) = (n+1)^2 <br>
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(He described it to me in 9-year-old words, not an equation, for what it’s worth.) And then, the other day, he told me that he’d figured this out:<br>
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n^2-1 = (n-1)*(n+1)<br>
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This kind of blows me away, because my brain just doesn’t work that way and I have to sit down and really think this stuff through—but it comes effortlessly to him.<br>
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So, two questions:<br>
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1. Do either of those patterns have a name? I know about, like, the Fibonacci Sequence and I think it would tickle him to know that he’s stumbled onto Someone’s Theorem or whatever.<br>
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2. What are some resources that can encourage / expand this kind of thinking? Obviously this is not my thing so I’m having trouble even finding the words to describe what I’m after. Remember that he’s just a little kid, so he’d probably lose interest if it’s dry and complicated. He just really digs the way that numbers are so orderly.tag:ask.metafilter.com,2016:site.297242Mon, 20 Jun 2016 18:35:31 -0800oceanmorningAt-Home Summer Math Program for Reluctant Teenager?
http://ask.metafilter.com/297088/At%2DHome%2DSummer%2DMath%2DProgram%2Dfor%2DReluctant%2DTeenager
We have a 15 year old (entering 10th grade) staying with us for the summer, who needs significant help with math. He worked pretty hard this past semester to bring his math grade up to a C - and I don't want him to lose that knowledge.
What can we do to work on his math skills this summer? Open to all ideas - books, online tutorials, games.tag:ask.metafilter.com,2016:site.297088Thu, 16 Jun 2016 06:56:15 -0800wearyaswaterMath education resources
http://ask.metafilter.com/297035/Math%2Deducation%2Dresources
I am aiming to create extracurricular programming for people of all ages (but I'm particularly focused on teens and adults) to illuminate the neat areas of math that aren't covered in school. (Graph theory, mobius strips, pascal's triangle, things like that.) However, I don't have a very official background in mathematics myself.
1) What resources can I use to teach myself about math in those areas, or math leading up to those areas?
2) What resources are out there for kids/teens/adults to increase their math awareness? Re: 1, I've been reading various books (texts on graph theory, etc.), using MIT OCW courses (Discrete math, multivariable calc, and linear algebra). Recommendations for specific math books are appreciated. I find Robin J. Wilson's Graph Theory textbook to be readable. Many other texts rely on familiarity with terms that I have not heard before. I would especially appreciate some sort of math glossary, or texts that, while they go deeply into the math, define their terms early on. Popular math books have been a good start, but I want to go deeper into the math.<br>
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Re 2: I've visited the Museum of Mathematics and love what they're doing.tag:ask.metafilter.com,2016:site.297035Tue, 14 Jun 2016 22:07:04 -0800azalea_chantHow much will it cost to run window air conditioner all year in PA?
http://ask.metafilter.com/296853/How%2Dmuch%2Dwill%2Dit%2Dcost%2Dto%2Drun%2Dwindow%2Dair%2Dconditioner%2Dall%2Dyear%2Din%2DPA
I am considering moving into an apartment where I cannot adjust my own heat, although management takes care to make sure everybody's happy in that department. But due to my health probs, I still may need to run the window air conditioner a LOT, most of the year. The air conditioner is appropriately sized - 8,000 BTU for 350 square feet (it's a small efficiency apartment.) I figured I may have to run it about 16 hours a day, most days of the year. I am assuming management will keep the heat 74 degrees in the day and 67 at night, and I prefer it 72 degrees max in the day and 65 max at nite.<br>
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(It is radiator heating. We are not allowed to touch the valves but can call management. I don't want to open windows because humidity/icy gales.)tag:ask.metafilter.com,2016:site.296853Fri, 10 Jun 2016 07:56:20 -0800serena15221Turns out I really like math...
http://ask.metafilter.com/296499/Turns%2Dout%2DI%2Dreally%2Dlike%2Dmath
How can I continue to study it? I'm a junior-and-a-half in college, earning a concurrent B.A. and M.A. in Computer Science. I started in physics at a different school, then transferred to my current school, and picked up the CS major while I was here. (As a transfer, I had to stick around for an extra year to fulfill all my prereqs anyway, and got enough financial aid/scholarships to take all the classes I needed.)<br>
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Something I didn't realize at my first school or until now (as I get close to graduation) is that I REALLY like math. Not the applied math that I mostly did at my very practical, untheoretical first school as a physics student, but the more abstract, proof-based math that I do at my new school. (New school is a top 5 school where everything is very theoretical.) I really really have fun in my math classes, and my only regret is that I didn't realize how much I liked it until now, because if I could go back 2-3 years, I would have majored in math here. I'm actually getting kind of depressed to wind down to graduation, because I want to take more math! <br>
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I especially liked my theoretical CS courses involving math-- advanced algorithms in particular was my favorite class. (So, discrete math.)<br>
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I know doing a PhD in math would be a totally different ballgame, and I have no idea if that's something I'd like to do. But I'd like to... find out? Is there a way to keep studying math? Should I try to get another bachelor's degree? (I'm thinking no but if it were free, I totally would.) Should I keep graduate school for math/computer science in the back of my mind? Would I do much math as a CS PhD?<br>
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My GPA is not incredible but pretty good (4.0 at first school, 3.5 average at first in second school due to poor study skills that I pulled up to a 3.7-3.8). I test well, so I think I could do well on the GRE. Don't have any research, but I have one year left to look for a project or a professor to work with. (I spent most of my time hunting down internships and "professionalizing" my resume which has made me appreciate academia more.) I wouldn't say I'm a math prodigy by any means-- I actually didn't think I was a math/science person until college, after a very bad public education-- but I feel pretty at home at the moment.<br>
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I do have a major fear of participating in class (though this has gotten better this year) and talking face-to-face with professors, which has always made me feel like I would really suck at graduate school. I guess it's something I'd like to overcome, but if my success depends on it, that's a bit scary for me.<br>
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I do well in my current math classes. I've been top of the class a few times, more frequently somewhere between the top and the upper quartile now that I'm around very talented people.tag:ask.metafilter.com,2016:site.296499Thu, 02 Jun 2016 00:56:51 -0800AnonymousCareer in IT and Computer Programming with zero knowledge?
http://ask.metafilter.com/296321/Career%2Din%2DIT%2Dand%2DComputer%2DProgramming%2Dwith%2Dzero%2Dknowledge
I'm fascinated with computers, robotics, and photography. Yet, there's something captivating about IT and Computer Programming. I'm almost finishing up my Social Science bachelor's degree (Sociology), which is pretty worthless from a marketable angle, little job offers. I would like to learn more about IT (Support Services for software) and Computer Programming as well, but I have no background in these two fields. Should I pursue a degree in either of these fields if I have no experience with math and computers? Furthermore, I would love to learn more about IT (Support Services) and Computer Programming, but I have poor math skills, in fact, algebra and division are difficult to do. What is IT and Computer Programming like in terms of mathematics? Are these difficult careers? I know that the two are a little different from Computer Science, which is more theoretical, similar to pure mathematics in a sense. Can someone who struggles at math pursue these kinds of careers? I'm willing to work extra hard to tackle the math bit, but I believe I might have a learning disability with math as well. I'm a gifted creative writer as well, but this isn't important when it comes to computers. I love to write essays, creative writing, think critically, be analytical, problem solve, which I think might help with this kind of career on some note. Does anyone have personal experiences with these careers, where math was a challenge? I originally wanted to be a Professor, Creative Writer, or a Research Librarian, but those jobs are difficult to live by, pay to pay, so to speak. I'd love to teach Philosophy, but the odds are slim, and road to a phD tenure and grad school is bloody tough, I have been told.<br>
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Are there excellent books for beginners on these topics and fields?<br>
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Any positive and constructive feedback would be most worthy and welcome -- it is good to look at both sides of the coin. Should I pursue this career route? Yes? No?tag:ask.metafilter.com,2016:site.296321Sat, 28 May 2016 15:12:06 -0800RearWindowShould we give daughter special education or let her be who she is?
http://ask.metafilter.com/296053/Should%2Dwe%2Dgive%2Ddaughter%2Dspecial%2Deducation%2Dor%2Dlet%2Dher%2Dbe%2Dwho%2Dshe%2Dis
We are troubled as to whether or not we should put our daughter in a math special education program. The school has said she needs it, but she is adamant that she does not want to be seen as different. She feels so strong about this, I feel like this is one of those turning points in life where I might make a huge mistake in what I do. My daughter is very gifted in music, has sung for hundreds of people in various venues, won awards, is in OPUS, has been in the theater and been selected as the favorite by the audience, plays musical instruments and won awards on those. She is also a public speaker. The reason I mention these, is to explain that she, as our daughter, has shown us who "she is" and the Mom in me says I should simply love her for who she is and not put such importance on school grades. I, myself, was an academic, so at first it was hard to see my daughter not get excellent grades in school. I would say she is a B student in other classes, but math is very hard for her. We have taken her to tutors, I've tried to help her, but she hates math and also is very challenged in it, when she does try. Sometimes she gets B's, sometimes C's, and sometimes, D's and F's.<br>
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Do I just not listen to her and put her in the special ed math class and tell her, "Look, sometimes you have to do things in life that you don't want. You need to pass the math class each year as you go through high school." OR do I just let go of the thing, stop trying to help her (which ends in arguments), not put her in that special class, and let her be who she wants to be, and if that is a performer of some kind, then so be it.<br>
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She is 13 so one of these days, before I know it, she will be out of the house and I want a relationship with my daughter. In the end, her happiness is what I want. I want her to feel good about herself and love her life.<br>
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Thanks.tag:ask.metafilter.com,2016:site.296053Sun, 22 May 2016 08:03:10 -0800lynnie-the-poohWhat are some mathematical or scientific principles of poker?
http://ask.metafilter.com/295371/What%2Dare%2Dsome%2Dmathematical%2Dor%2Dscientific%2Dprinciples%2Dof%2Dpoker
I'm trying to get a list of things (equations, theories, etc) we know about poker or gambling in general in terms of scientific or mathematic principles. It can't just be game theory. it's got to be specific aspects of it. And I mean ANY aspects of it. Hot hands. Beginner's luck. Inside straights.tag:ask.metafilter.com,2016:site.295371Thu, 05 May 2016 07:40:30 -0800rileyray3000Remedial Maths for Grownups
http://ask.metafilter.com/295163/Remedial%2DMaths%2Dfor%2DGrownups
What are good (and preferably free) resources for self-teaching high school level mathematics? Snowflakes etc. below the fold. I have a complicated relationship with maths. As a young critter I was good with numbers, and until the end of 8th grade was near the top of my class, could complete most tasks asked of me in my head, and made it a hobby to find errors in the answer sections of textbooks. <br>
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When I hit 9th grade I had a clumsily managed transition skipping up into a 10th grade "accelerated" math class. I wasn't given bridging work, my teacher had no interest in helping me catch up on concepts I was unfamiliar with (and seemed to take an active dislike to me but that's another story), and being 14 I didn't have the wits to research my way out of the problem. I crashed and burned, and was made to repeat 10th grade maths the following year in the lowest skilled group ("veggie maths" we call it cruelly and colloquially here in Australia). Again, being 14 and not that emotionally developed, I got the impression my former facility with numbers was an illusion, I was dumb, and promptly gave up on STEM in general and went all-out on the arts.<br>
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FFWD to today, I'm moderately successful as a musician/artist/teacher/academic support tutor, and have proved to myself the dumbness thing was incorrect (yay self-esteem!), however I greatly regret, and have a bunch of insecurity around my loss of mathematics, and 20-ish years later I want it back goddammit. <br>
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Please help the ghost of 14 year old math-nerd me get back on the horse.<br>
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(If it's relevant my last experience of mathematics education was in the mid 1990s public high school system of Victoria, Australia)tag:ask.metafilter.com,2016:site.295163Sat, 30 Apr 2016 08:55:33 -0800threecheesetreesCounting 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 lady