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94 posts tagged with math *and* statistics.

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## Too Many Strata To Sample

I have multiple independent variables that I want to stratify my sampling across, but the result would be way more strata than I can sample. Is there a way to stratify across different character states for each independent variable without creating strata for the interactions of each? Example inside. [more inside]

## I was told there would be no math.

I've crossed a bunch of plants with one another, and now have a bunch of berries on those plants. Each berry can contain way more seeds than I have room to pot up and grow out individually, so I'm trying to find the point of diminishing returns, where potting up additional seedlings stops giving me new and interesting results, but my math background is inadequate. [more inside]

## Math problem alert: NCAA Magic or Unsurprising?

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!

## Statistical framing of the engineering and extremism article

Reading this 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. [more inside]

## Can an exact measurement ever be statistically insignificant?

I am dubious of a colleagueâ€™s assertions about statistics. [more inside]

## Probability distributions and their practical applications

I am looking for a resource that lists probability distributions and their common real-world applications. For example, I'd expect to see: Lognormal - daily returns in the stock market. Poisson - failure rates for mechanical equipment, ... [more inside]

## Math Problem

Please help with this probability related math problem. [more inside]

## Help me understand the concept of "85th Percentile."

I am part of a group working on a policy document for the mitigation of traffic issues (e.g. speeding). Stakeholders are having a hard time with a particular criteria which reads as follows: "85th percentile speed is in excess of the signed speed limit by 5 mph or more." [more inside]

## Math, sweet sweet math

I have a set of data: D(t). 5000 samples. Scatter-graphing makes some patterns clear (D-mean increases with t, for instance). D and t are always positive. I want to characterize these, statistically. [more inside]

## Statistics Book for an interested teen

My teen aged niece has suddenly found a strong interest in statistics. What book would you recommend for a 14 year old who has good, but not advanced, math skills?

## Help! Can I normalize statistical coefficients?

With deadline looming, stats consultant has bailed. Simple queries need resolution. Help?
I am working on a data graphic that involves statistical calculations about survival rates for startup businesses, correlated with certain tangible and intangible factors. The raw data (about survival/closure/merger outcomes) has already been investigated, and the original researchers (who are awesome) have generated some interesting correlations using univariate regressions and Cox regressions. For my output I am relying on their statistically significant findings, wanting to create comparisons among the univariate coefficients. Not sure my methods are kosher and would appreciate consultation. Avalanche inside. [more inside]

## What are inter-disciplinary and atypical uses for math MSc?

I have just completed my MSc in mathematics in Europe. I do enjoy math, but I spent my uni years feeling like a autodidact hippie marooned on an island full of Mr and Mrs I-Want-A-Good-Job. My main interests revolve around humanities (literature/history/anthropology) and economics (but not finance), and instead of starting a "stable" well-paying career I dream about something inter-disciplinary. I am very open to earning little money and relocating just to do kind of work that engages those skills. What are some random uses of my degree? [more inside]

## 2 problems of combinations and permutations.

How many unique ways are there to put X rocks into Y boxes?
(Given two different sets of attributes for both the rocks and the boxes.) [more inside]

## Chance of event with small sample size, based on larger related sample?

Can/how can one improve the estimate for a chance of an event with a small historical sample size by utilizing the chance of a related event with a large historical sample size? Example and half-assed guess inside. [more inside]

## Becoming Fluent in Predictive Analytics

I work in a University managing the broad based direct mail, email and calling programs. I have zero undergrad or graduate experience with math, business or the social sciences. (Aka, I can write a really nice essay...) I would like to chart a path to being recognized as an expert in predictive analytics. [more inside]

## Career advice for math major (also competent programmer)?

I like math. Programming is OK, but I don't want to make it my thing. What careers should I be looking at? (Special snowflake details inside.) [more inside]

## Find standard deviation in Excel, but first develop a labor-saving trick

Help me with statistics and Excel. Especially help me if you know any labor saving methods. I want the median, mean and standard deviation for the average price of all items sold, but my spreadsheet-full-of-data doesn't tell me the price of each sale -- just the average price per store, and the number sold at that store. Something like this: [more inside]

## Returning to grad school after 2 year hiatus

So I'm beginning a statistics PhD program this fall and I'm concerned that my math skills have gotten rusty since I haven't done anything related for the past two years. I've been working as an actuary since I graduated college but I don't do that much math--mostly a lot of programming. Has anybody been in a similar situation to me? How was the adjustment for you? I'm considering retaking advanced calculus and linear algebra during my first year (probably next summer before I take 2nd year advanced courses) just to refresh myself again. I'm aware some people may think this is kind of pathetic but I'd rather be safe than sorry. Besides, it's only my first year. Is this frowned upon? [more inside]

## Learning Statistics for the Social Sciences 101 paperlessly

I'm running into trouble with my statistics course. I'm just getting up to t statistics for independent measures research design. My problems are:
1. I'm going through a lot of paper
2. I need to keep all my calculations better organized as a do them
3. I'm flipping back and forth between my book, an online version of the book, and another screen so that I can reference as much material as possible at once. I'm thinking some kind of basic statistics calculator spreadsheet (or any other format) would be in order. Can anybody direct me towards one? [more inside]

## Fallacies and Errors in Inferential Statistics

I have recently been introduced to the concept of pseudoreplication as a mistake that people often make when using inferential statistics to evaluate treatment outcomes. My field (evolutionary and conservation biology) makes heavy use of inferential statistics, including techniques that are vulnerable to pseudoreplication, yet nowhere in my formal education have I been taught about how poor experimental design and lack of statistical rigor can lead to fallacies like this. My personal statistical proficiency is poor, but I am working to remedy that. To that end, could folks help me by identifying and ideally explaining whatever other potential pitfalls you can think of, and explaining how they can be avoided through careful experimental design and data-analysis?

## What does a professional statistician do?

(Good) jobs involving probability and statistics other than math teacher or actuary? [more inside]

## How to solve a complex statistics problem with a script?

In this game, you roll a number of six-sided dice to get a

**total**. The total is either the highest single die result, or the sum of any multiples rolled, whichever is higher. For example: If I roll three dice and get a 3, 4, and 6, my total is 6. But if I roll a 4, 4, and 6, my total is 8, the sum of the two 4s. What I want to find out is the mean, median, mode, and standard deviation of the possible totals given N dice. How might I create a simple script to compute this? [more inside]## What should my sample size be?

Say that I have a bag which contains 100 balls and every ball in the bag should be red, but it's possible that one or more of these balls is the wrong colour. How many balls should I look at to be 90% sure that all the balls are red? Or 95%? Or 99.9%? Talk me through how to work this out, please?

## Practice Probability Word Problems

What great books or resources are there for practicing probability word problems such as for standardized tests like the GRE? [more inside]

## What are the odds that two randomly selected people share the same bank PIN?

Statisticsfilter: Given available information about the distribution of self-selected 4-digit passwords (specifically banking PINs), is it possible to calculate the probability of two randomly selected individuals having the same PIN? If so, what're the odds? [more inside]

## How do I calculate the probability of a specific sum of repeated die rolls?

I'm looking to learn how to calculate probabilities for a multi-round dice game. I've researched this question some, and it looks like I might need to know how to use the multinomial distribution, but I can't find any good introductions. Please point me to the most layman-accessible educational material on this subject, and help me to help myself. [more inside]

## Too much noise in my data

Putting on the math signal: calling the statistics-literate. Trying to change my weight/body composition and track progress in a useful way, but I'm having trouble separating normal daily variation from actual real change. [more inside]

## Pocket Anthropology

Is there a way to find out approximately when I left this wad of money in my (very old) jacket pocket, using statistics and date/number info from the bills? What would be the minimum number of bills needed for such a thing?

## How to model the accident rate on a certain stretch of road

How could I approach modeling the number of accidents on a certain stretch of road? I've got some semi-ecological approaches in mind but no idea if they're workable. Are there standard approaches to this sort of problem? [more inside]

## Identifying urban centers using an algorithm based on topological prominence

Calling geographers: has anyone applied the idea of topological prominence to population density? [more inside]

## Bathrooms and Statistics

My workplace has 3 small bathrooms. It seems to me that if I go to use one of them, and it's occupied, there is a statically higher chance the 2nd and even 3rd bathroom will be occupied (vs the chance that they would be occupied if the 1st one was not). Is it true? [more inside]

## When calculating a statistical average, is it reasonable to remove outliers?

When calculating a statistical average, is it reasonable to remove outliers? [more inside]

## Probability Question

Probability Question [more inside]

## I'm a rank amateur

What are some basic math concepts I can use to understand and develop a ranking system? [more inside]

## Need help with a probability question

Can someone help with a probability question? [more inside]

## Shouldn't a point estimate be the midpoint of its confidence interval?

Shouldn't a point estimate be in the center of its confidence interval? [more inside]

## Calculus? Is that it?

## What statistical analysis of historical prices would be useful for a buyer?

What statistical analysis of historical prices would be useful for a buyer? [more inside]

## Math skills for 300-level statistics?

I'm about to start a 300-level Statistics course, but my math skills are very rusty. How can I quickly rejuvenate my old skills? [more inside]

## When do I look for non-academic jobs?

When do I look for non-academic jobs if I'm trying to transition out of academia, and which jobs do I look for? (I have a math PhD.) [more inside]

## How do I fairly assign partial credit?

How do I assign partial credit consistently? [more inside]

## Textbooks on data mining techniques / statistical analysis on large data sets?

Textbooks on data mining techniques / statistical analysis on large data sets? [more inside]

## Clustering Discrete Data

Help me figure out how to do cluster analysis on discrete data. [more inside]

## A variation on the birthday paradox

I have 232 facebook friends, and six of them share a birthday in common (not 6 different pairs of people on the same birthday, but 6 out of the 232 were born on the 17th of July. Now, I know it only takes 23 random people to get a 50% chance of at least ONE birthday collision, but how the heck do I figure out the odds on this one? Is this a significant anomaly, or reasonably expected? My one stats class was entirely too long ago....

## How do I go about finding a plateau within a set of numbers?

How do I go about finding a plateau within a set of numbers? [more inside]

## Seeking advice/help about statistical tests of significance.

I have a wonderfully large dataset that I'm working with for a long-term project. I am analyzing a small section the dataset for my masters thesis. In meeting with my thesis advisor last week, she suggested I run some statistical tests of significance on the 4 tables I'm working with. She knows that I am yet to be versed in quantitative analysis methods (I've done solely qualitative work thus far) and that I'm under a massive time crunch to get this done. She suggested I seek help from others, as she doesn't want me to get bogged down with figuring out this step, and would rather I concentrate on analyzing the other aspects of this data. To this end, I'm wondering if somebody might be able to suggest the best type of test of significance to run, the easiest way to run it, and a good, simple resource for what the resultant values mean? [more inside]

## What's higher level statistics like?

Math-related career advice requested: is work in higher level statistics compatible with an imaginative-type thinker or would it be total hell? [more inside]

## What basic statistics concepts do I need to understand web analytics?

I'm registered for a Web Analytics class. A prerequisite is "Familiarity with basic concepts of statistics." I'm not a math person and never studied statistics. Which basic statistics concepts should learn before this class? Are there any comic books, videos, or fun resources that would help me learn? [more inside]

## Help me sample accurately!

Please provide me with an *effective*, and statistically sound, table/chart listing suggested sample size guidance for associated population size [more inside]

## Math/Stats: help me analyze a data set and determine the values that created it

Mathematics / Statistics Filter: I have some pairs of numbers that are the result of a process. Given just that data set, and a rule that relates them, can you determine the integer values that could have resulted in those sets? [more inside]

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