Linked Questions

165
votes
76answers
204k views

Statistics Jokes

Well, we've got favourite statistics quotes. What about statistics jokes?
79
votes
9answers
16k views

Regarding p-values, why 1% and 5%? Why not 6% or 10%?

Regarding p-values, I am wondering why $1$% and $5$% seem to be the gold standard for "statistical significance". Why not other values, like $6$% or $10$%? Is ...
27
votes
17answers
5k views

How to describe statistics in one sentence?

When I first started learning statistics, procedures like the t-test, ANOVA, chi-squared and linear regression each appeared to be very different creatures. But now I realise these procedures each do ...
71
votes
4answers
26k views

When to use Fisher and Neyman-Pearson framework?

I've been reading a lot lately about the differences between Fisher's method of hypothesis testing and the Neyman-Pearson school of thought. My question is, ignoring philosophical objections for a ...
38
votes
8answers
19k views

How to test hypothesis of no group differences?

Imagine you have a study with two groups (e.g., males and females) looking at a numeric dependent variable (e.g., intelligence test scores) and you have the hypothesis that there are no group ...
57
votes
4answers
16k views

How small a quantity should be added to x to avoid taking the log of zero?

I have analysed my data as they are. Now I want to look at my analyses after taking the log of all variables. Many variables contain many zeros. Therefore I add a small quantity to avoid taking the ...
42
votes
8answers
2k views

Are all models useless? Is any exact model possible — or useful?

This question has been festering in my mind for over a month. The February 2015 issue of Amstat News contains an article by Berkeley Professor Mark van der Laan that scolds people for using inexact ...
25
votes
7answers
1k views

Distribution hypothesis testing - what is the point of doing it if you can't “accept” your null hypothesis?

Various hypothesis tests, such as the $\chi^{2}$ GOF test, Kolmogorov-Smirnov, Anderson-Darling, etc., follow this basic format: $H_0$: The data follow the given distribution. $H_1$: The data do not ...
27
votes
5answers
8k views

Is there an explanation for why there are so many natural phenomena that follow normal distribution?

I think this is a fascinating topic and I do not fully understand it. What law of physics makes so that so many natural phenomena have normal distribution? It would seem more intuitive that they would ...
36
votes
1answer
8k views

Why do my p-values differ between logistic regression output, chi-squared test, and the confidence interval for the OR?

I have built a logistic regression where the outcome variable is being cured after receiving treatment (Cure vs. No Cure). All ...
27
votes
4answers
2k views

Pitfalls in experimental design: Avoiding dead experiments

I've come across this quote numerous times: To consult the statistician after an experiment is finished is often merely to ask him to conduct a post mortem examination. He can perhaps say what ...
6
votes
8answers
3k views

What's the name for this statistical fallacy?

I was told an anecdote by someone today who was trying to prove a point regarding safety. They said "50 people have been living in [area a] for the past two years one year (apparently I remembered the ...
16
votes
5answers
2k views

What is effect size… and why is it even useful?

I have an introductory-graduate-level statistics background (assume I know mathematical statistics and probability at an undergraduate level (e.g., Wackerly et al., Ross' Probability), and have some ...
19
votes
4answers
25k views

How to test if my distribution is multimodal?

When I plot a histogram of my data, it has two peaks: Does that mean a potential multi-modal distribution? I ran the dip.test in R (...
12
votes
4answers
530 views

Is any quantitative property of the population a “parameter”?

I'm relatively familiar with the distinction between the terms statistic and parameter. I see a statistic as the value obtained from applying a function to the sample data. However, most examples of ...
9
votes
2answers
8k views

When to use Student's or Normal distribution in linear regression?

I am looking at some problems, and in some, to test the coefficients, sometimes I see people using Student's distribution, and sometimes I see Normal distribution. What is the rule?
18
votes
1answer
2k views

Central limit theorem and the law of large numbers

I have a very beginner's question regarding the Central Limit Theorem (CLT): I am aware that the CLT states that a mean of i.i.d. random variables is approximately normal distributed (for $n \to \...
19
votes
3answers
3k views

What is the importance of the function $e^{-x^2}$ in statistics?

In my calculus class , we encountered the function $e^{-x^2}$, or the "bell curve", and I was told that it has frequent applications in statistics. Out of curiosity, I want to ask: Is the function $...
5
votes
5answers
2k views

Is it appropriate to examine an interaction effect that is almost statistically significant?

I am conducting a 2x2 within-subjects design. When I plot my results it appears that there will be an interaction between my variables but unfortunately none is emerging p=0.08. I find it a shame that ...
11
votes
3answers
5k views

When is a fixed effect truly fixed?

Consider a linear unobserved effects model of the type: $$y_{it} = X_{it}\beta + c_{i} + e_{it}$$ where $c$ is an unobserved but time-invariant characteristic and $e$ is an error, $i$ and $t$ index ...
8
votes
1answer
9k views

Omitted variable bias in linear regression

I have a philosophical question regarding omitted variable bias. We have the typical regression model (population model) $$ Y= \beta_0 + \beta_1X_1 + ... + \beta_nX_n + \upsilon, $$ where the ...
12
votes
3answers
429 views

Is it better to select distributions based on theory, fit or something else?

This is bordering on a philosophical question, but I am interested in how others with more experience think about distribution selection. In some cases it seems clear that theory might work best (mice ...
20
votes
2answers
3k views

Can we see shape of normal curve somewhere in nature?

I do not want to know if some phenomena in nature have normal distribution, but whether we can somewhere see shape of normal curve as we can see it for example in Galton box. See this figure from ...
8
votes
4answers
576 views

Choosing a regression model

How can one objectively (read "algorithmically") select an appropriate model for doing a simple linear least-squares regression with two variables? For example, say the data seem to show a quadratic ...
4
votes
3answers
3k views

Ways to overcome small number of survey responses

For one of my academic project I ran a sample survey. But unfortunately the respondents were not very proactive & I get just 25 responses for my study. With this small response I guess I can't do ...
9
votes
2answers
632 views

Famous data visualizations [duplicate]

I am looking for famous, historical, beautiful, impressive, or otherwise noteworthy visualizations based on statistical concepts. I think of examples along the lines of Florence Nightingale's ...
3
votes
2answers
171 views

What really happens when we transform the data using $f(x) = \sin(\sqrt{x})$?

I need to perform a two-way ANOVA on my data ($Y$: sleeping hours). My data is quite normal $p$-value = $0.07$ with Shapiro-Wilk test but when I run the normality test for my residual, $p$-value is ...
6
votes
2answers
1k views

Using multiple comparisons corrections in Fisher p-value framework

I am wary of stepping into the civil war between Fisher vs Neyman-Pearson interpretations of $p$-value (which has been well elucidated here and here), but I've been pondering a question that I keep ...
9
votes
2answers
532 views

Can a narrow confidence interval around a non-significant effect provide evidence for the null?

It is obviously fallacious to assume that failure to reject the null implies that the null is true. But in a case where the null is not rejected and the corresponding confidence interval (CI) is ...
1
vote
1answer
1k views

Intuition for Gamma-Poisson / Negative Binomial

I have a data set which intuitively seems Poisson-like, but it's overdispered. So I'm investigating negative binomial. From this question and this page I understand one way of viewing this is to ...
4
votes
2answers
287 views

Significance in Longitudinal Data

I feel like this question has a very silly (simple) answer, so I apologize. I have a data set that only has 5 points 41.9 32.2 113.3 110.2 102.6 Clearly ...
0
votes
2answers
602 views

Using MLE to determine parameters for QQ plot

I just started playing around with a credit fraud dataset that I found online. I noticed that one of the variables looked something like this: Hey, that looks like a 3 parameter log-normal ...
5
votes
1answer
584 views

How to choose between exponential and gamma distributions

I have same data and I would like to choose a model for it. To start with I fit an exponential distribution and a gamma distribution. Now I wanted to do a simple likelihood ratio test . However, I ...
1
vote
2answers
1k views

Comparing patient and control group results of a survey

I have data from a survey given to a patient group and control group. Both groups completed the same exact survey (Likert scale). One group has an n of only 5 or 6, the other n was about 15. What ...
3
votes
1answer
471 views

Likelihood based model selection

Let's say I got a set of models $M = \{M_1, M_2, \dots M_n\}$. Now say I got some data $x$ and I would like to know, which model represents the data best. I know how to calculate the likelihood $L(\...
3
votes
1answer
120 views

Can you determine if variances are equal when quartiles are similar?

I am comparing 2 different data sets. I have broken down each set into quartiles. I am looking at the percentage of increase between the quartiles (example there was a 125 percent increase between ...
2
votes
1answer
139 views

If my normality test is non-significant, am I safe to use the t-test?

I took a 30 unit sample from a population. The sample distribution resulted to be normal. Can I state that the population distribution is normal too? If so, with what level of confidence?
0
votes
1answer
104 views

how to choose a transformation for left heavy tailed data due to arbitrary upper limit imposed by experimenter?

I have two vectors that look like this: I would like to make a significance test on the paired differences between the two vectors, as well as measure association. The process of data generation is "...
4
votes
1answer
41 views

Expanding initial sample when the result isn't significant

This inspiring answer describes a variant of hypothesis, and I want to analysis its property further. Basically, it considers a two-sided test and interprets the $p$-value as a measure of how strong ...
0
votes
1answer
93 views

Hypothesis test of mean between groups with dependencies and pairing

I have two groups with small number of n (less than 10) where some observations are replicates for each other, some are paired difference observations, and some are completely independent. For example:...
-1
votes
1answer
49 views

Is there non-distribution (without any distribution rule) data?

My classmate told me: Any data in this world fit a kind of distribution I am just newbie in statistics.I just know normal,...
0
votes
0answers
38 views

Distribution for semi open interval

I have an application where I get back the time to perform an operation, the times are in the interval ]0:inf[ and I have this crazy idea. Lets say I know the mean ...