175
votes
20answers
52k views

Python as a statistics workbench

Lots of people use a main tool like Excel or another spreadsheet, SPSS, Stata, or R for their statistics needs. They might turn to some specific package for very special needs, but a lot of things can ...
163
votes
24answers
54k views

Making sense of principal component analysis, eigenvectors & eigenvalues

In today's pattern recognition class my professor talked about PCA, eigenvectors & eigenvalues. I got the mathematics of it. If I'm asked to find eigenvalues etc. I'll do it correctly like a ...
144
votes
54answers
53k views

What is your favorite “data analysis” cartoon?

This is one of my favorites: One entry per answer. This is in the vein of the Stack Overflow question What’s your favorite “programmer” cartoon?. P.S. Do not hotlink the cartoon without the site's ...
139
votes
15answers
23k views

The Two Cultures: statistics vs. machine learning?

Last year, I read a blog post from Brendan O'Connor entitled "Statistics vs. Machine Learning, fight!" that discussed some of the differences between the two fields. Andrew Gelman responded favorably ...
119
votes
132answers
29k views

Famous statistician quotes

What is your favorite statistician quote? This is community wiki, so please one quote per answer.
112
votes
16answers
32k views

Why square the difference instead of taking the absolute value in standard deviation?

In the definition of standard deviation, why do we have to square the difference from the mean to get the mean (E) and take the square root back at the end? Can't we just simply take the absolute ...
111
votes
43answers
9k views

What are common statistical sins?

I'm a grad student in psychology, and as I pursue more and more independent studies in statistics, I am increasingly amazed by the inadequacy of my formal training. Both personal and second hand ...
108
votes
8answers
25k views

Is Facebook coming to an end?

Recently, this paper has received a lot of attention (e.g. from WSJ). Basically, the authors conclude that Facebook will lose 80% of its members by 2017. They base their claims on an extrapolation ...
99
votes
6answers
7k views

Is $R^2$ useful or dangerous?

I was skimming through some lecture notes by Cosma Shalizi (in particular, section 2.1.1 of the second lecture), and was reminded that you can get very low $R^2$ even when you have a completely linear ...
95
votes
14answers
25k views

Amazon interview question—probability of 2nd interview

I got this question during an interview with Amazon: 50% of all people who receive a first interview receive a second interview 95% of your friends that got a second interview felt they had a good ...
94
votes
15answers
16k views

Bayesian and frequentist reasoning in plain English

How would you describe in plain English the characteristics that distinguish Bayesian from Frequentist reasoning?
89
votes
8answers
13k views

Detecting a given face in a database of facial images

I'm working on a little project involving the faces of twitter users via their profile pictures. A problem I've encountered is that after I filter out all but the images that are clear portrait ...
88
votes
7answers
31k views

What is the difference between “likelihood” and “probability”?

The wikipedia page claims that likelihood and probability are distinct concepts. In non-technical parlance, "likelihood" is usually a synonym for "probability," but in statistical usage there is a ...
81
votes
6answers
8k views

Explaining to laypeople why bootstrapping works

I recently used bootstrapping to estimate confidence intervals for a project. Someone who doesn't know much about statistics recently asked me to explain why bootstrapping works, i.e., why is it that ...
81
votes
7answers
6k views

Why does a 95% CI not imply a 95% chance of containing the mean?

It seems that through various related questions here, there is consensus that the "95%" part of what we call a "95% confidence interval" refers to the fact that if we were to exactly replicate our ...
78
votes
12answers
16k views

Is normality testing 'essentially useless'?

A former colleague once argued to me as follows: "we usually apply normality tests to the results of processes that, under the null, generate random variables that are only asymptotically or ...
76
votes
10answers
19k views

Is there any reason to prefer the AIC or BIC over the other?

The AIC and BIC are both methods of assessing model fit penalized for the number of estimated parameters. As I understand it, BIC penalizes models more for free parameters than does AIC. Beyond a ...
75
votes
5answers
39k views

Difference between logit and probit models

What is the difference between the logit and the probit model? I'm more interested here in knowing when to use logistic regression, and when to use probit. If there's any literature which define it ...
75
votes
5answers
12k views

What is the intuition behind beta distribution?

Disclaimer: I'm not a statistician but a software engineer. Most of my knowledge in statistics comes from self-education, thus I still have many gaps in understanding concepts that may seem trivial ...
72
votes
16answers
4k views

How to annoy a statistical referee?

I recently asked a question regarding general principles around reviewing statistics in papers. What I would now like to ask, is what particularly irritates you when reviewing a paper, i.e. what's the ...
71
votes
24answers
5k views

Locating freely available data samples

I've been working on a new method for analyzing and parsing datasets to identify and isolate subgroups of a population without foreknowledge of any subgroup's characteristics. While the method works ...
66
votes
14answers
21k views

Does Julia have any hope of sticking in the statistical community?

I recently read a post from R-Bloggers, that linked to this blog post from John Myles White about a new language called Julia. Julia takes advantage of a just-in-time compiler that gives it wicked ...
66
votes
26answers
24k views

What is the best introductory Bayesian statistics textbook?

Which is the best introductory textbook for Bayesian statistics? One book per answer, please.
65
votes
21answers
12k views

Resources for learning R [duplicate]

I'm interested in learning R on the cheap. What's the best free resource/book/tutorial for learning R?
63
votes
6answers
14k views

Does causation imply correlation?

Correlation does not imply causation, as there could be many explanations for the correlation. But does causation imply correlation? Intuitively, I would think that the presence of causation means ...
62
votes
54answers
54k views

Statistics Jokes

Well we've got favourite statistics quotes. What about statistics jokes? So, what's your favourite statistics joke?
62
votes
10answers
23k views

How should I transform non-negative data including zeros?

If I have highly skewed positive data I often take logs. But what should I do with highly skewed non-negative data that include zeros? I have seen two transformations used: log(x+1) which has the ...
61
votes
21answers
25k views

R vs SAS, why is SAS preferred by private companies?

I learned R but it seems that companies are much more interested in SAS experience. What are the advantages of SAS over R?
61
votes
5answers
2k views

Essential data checking tests

In my job role I often work with other people's datasets, non-experts bring me clinical data and I help them to summarise it and perform statistical tests. The problem I am having is that the ...
61
votes
9answers
154k views

What is the meaning of p values and t values in statistical tests?

After taking a statistics course and then trying to help fellow students, I noticed one subject that inspires much head-desk banging is interpreting the results of statistical hypothesis tests. It ...
60
votes
10answers
28k views

What are the differences between Factor Analysis and Principal Component Analysis

It seems that a number of the statistical packages that I use wrap these two concepts together. However, I'm wondering if there are different assumptions or data 'formalities' that must be true to use ...
60
votes
7answers
20k views

What's the difference between a confidence interval and a credible interval?

Joris and Srikant's exchange here got me wondering (again) if my internal explanations for the the difference between confidence intervals and credible intervals were the correct ones. How you would ...
59
votes
12answers
8k views

What's wrong with XKCD's Frequentists vs. Bayesians comic?

This xkcd comic (Frequentists vs. Bayesians) makes fun of a frequentist statistician who derives an obviously wrong result. However it seems to me that his reasoning is actually correct in the ...
58
votes
16answers
14k views

Most interesting statistical paradoxes

Because I find them fascinating, I'd like to hear what folks in this community find as the most interesting statistical paradox and why.
58
votes
6answers
6k views

How to efficiently manage a statistical analysis project?

We often hear of project management and design patterns in computer science, but less frequently in statistical analysis. However, it seems that a decisive step toward designing an effective and ...
58
votes
1answer
24k views

Interpretation of R's lm() output

the help pages in R assume I know what those numbers mean. I don't :) I'm trying to really intuitively understand every number here. I will just post the output and comment on what I found out. There ...
57
votes
5answers
5k views

What skills are required to perform large scale statistical analyses?

Many statistical jobs ask for experience with large scale data. What are the sorts of statistical and computational skills that would be need for working with large data sets. For example, how about ...
57
votes
4answers
8k views

Which “mean” to use and when?

So we have arithmetic mean (AM), geometric mean (GM) and harmonic mean (HM). Their mathematical formulation is also well known along with their associated stereotypical examples (e.g., Harmonic mean ...
56
votes
7answers
64k views

How to summarize data by group in R?

I have R data frame like this: ...
56
votes
11answers
28k views

What is the difference between data mining, statistics, machine learning and AI?

What is the difference between data mining, statistics, machine learning and AI? Would it be accurate to say that they are 4 fields attempting to solve very similar problems but with different ...
56
votes
6answers
6k views

Model for predicting number of Youtube views of Gangnam Style

PSY's music video "Gangnam style" is popular, after a little more than 2 months it has about 540 million viewers. I learned this from my preteen children at dinner last week and soon the discussion ...
55
votes
6answers
24k views

How to understand degrees of freedom?

From Wikipedia, there are three interpretations of the degrees of freedom of a statistic: In statistics, the number of degrees of freedom is the number of values in the final calculation of a ...
55
votes
9answers
17k views
54
votes
19answers
3k views

What are some valuable Statistical Analysis open source projects?

What are some valuable Statistical Analysis open source projects available right now? Edit: as pointed out by Sharpie, valuable could mean helping you get things done faster or more cheaply.
53
votes
19answers
4k views

What is the single most influential book every statistician should read?

If you could go back in time and tell yourself to read a specific book at the beginning of your career as a statistician, which book would it be?
51
votes
15answers
3k views

Rules of thumb for “modern” statistics

I like G van Belle's book on Statistical Rules of Thumb, and to a lesser extent Common Errors in Statistics (and How to Avoid Them) from Phillip I Good and James W. Hardin. They address common ...
51
votes
11answers
9k views

Are large data sets inappropriate for hypothesis testing?

In a recent article of Amstat News, the authors (Mark van der Laan and Sherri Rose) stated that "We know that for large enough sample sizes, every study—including ones in which the null hypothesis of ...
51
votes
14answers
3k views

Complete substantive examples of reproducible research using R

The Question: Are there any good examples of reproducible research using R that are freely available online? Ideal Example: Specifically, ideal examples would provide: The raw data (and ideally ...
50
votes
19answers
6k views

Free statistical textbooks

Are there any free statistical textbooks available?
49
votes
28answers
9k views

What book would you recommend for non-statistician scientists?

What book would you recommend for scientists who are not statisticians? Clear delivery is most appreciated. As well as the explanation of the appropriate techniques and methods for typical tasks: ...

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