37k views

### Practical thoughts on explanatory vs. predictive modeling

Back in April, I attended a talk at the UMD Math Department Statistics group seminar series called "To Explain or To Predict?". The talk was given by Prof. Galit Shmueli who teaches at UMD's Smith ...
8k views

### Misunderstanding a P-value?

So I've been reading a lot about how to correctly interpret a P-value, and from what I've read, the p-value says NOTHING about the probability that the null hypothesis is true or false. However, when ...
6k views

### What follows if we fail to reject the null hypothesis? [duplicate]

What conclusions can we draw if $p>\alpha$? Does not rejecting the $H_0$ mean anything?
11k views

### Many p-values are equal to 1 after Bonferroni correction; is it normal?

I have behavioral data for 10 animals that I studied at two different times of day, AM and PM. I am looking to see if there is a significant difference in 8 different behaviors at AM vs. PM. I have ...
15k views

### p-value correction for multiple t-tests?

My dataset consists of $n$ genes, each of them described by a vector of expression values, $5$ for "healthy" individuals, and $5$ for "unhealthy" individuals. I am going to run $n$ t-tests (one for ...
4k views

### Is there a consensus on adjusting alpha for multiple contrasts if the main effect is significant?

After talking to a couple of statisticians, reading some book sections, internet articles, and forums like this, I am still unclear about multiplicity adjustments of post hoc tests and contrasts. Let'...
2k views

### Is there a multiple testing problem when performing t-tests for multiple coeffcients in linear regression?

This question comes from a discussion on the recent post by @rvl It's all in the family; but do we include the in-laws too? Here's a common scenario that I've seen many times. A researcher runs a ...
6k views

### Implementing chi-square in python and testing on scipy's poisson and norm variates

I need to implement Pearson's chi-squared test to test random variates. But I get very different results using different sequence length,degrees of freedom or even seeds. Only a few times sequences ...
613 views

### Extent of multiple testing correction

A bit of a strange question. In my fourth year biostatistics class today, we were discussing when and when not to use multiple testing correction, and the professor made an offhand comment. He asked ...
1k views

### Controlling FWER using minP/maxT methods

A common approach for controlling the FWER in genomics analysis is the so-called minP/maxT procedure. See, for example: Dudoit, S., Shaffer, J.P., and Boldrick, J.C. (2003). Multiple Hypothesis ...
517 views

### What is the cause of the multiple comparisons problem?

I understand the intuition behind the MCP but I'm having trouble pinpointing exactly the cause, what is it that should be avoided, or at least accounted for. In its most blunt definition, I agree ...
1k views

### Correcting for multiple comparisons - same test on different data, vs different test on same data

I have a list of p-values and want to correct for multiple comparisons, i.e. control for the accumulation of false positives. In general, should I adjust my approach depending on whether the p-values ...
367 views

### Why bother looking at an omnibus ANOVA when I have a priori hypotheses about group differences?

I am examining three independent groups that were measured on a continuous outcome variable. I have a priori belief that the result should be Group 1 < Group 2 < Group 3. I've been told to do an ...