Linked Questions

6 votes
6 answers

Comparing two, or more, independent paired t-tests

Can we compare the results from two, or more, independent paired t-tests? For example: I want to test if drug 1 and drug 2 are effective to reduce weight. I have a control group (that will consume a ...
Numbermind's user avatar
14 votes
5 answers

Does p-value ever depend on the alternative?

Our tag definition of the $p$-value says In frequentist hypothesis testing, the $p$-value is the probability of a result as extreme (or more) than the observed result, under the assumption that the ...
Richard Hardy's user avatar
9 votes
5 answers

Why is the p-value defined the way it is (as opposed to a more intuitive measure)?

As I understand it the p-value for some hypothesis H and some test-statistic T is defined as the probability of observing a test-statistic T' which is at least as extreme as T, conditional on H being ...
amarai's user avatar
  • 101
15 votes
4 answers

Difference/relationship between power and significance

What is the conceptual difference between statistical power and statistical significance? Are they the same? Is one used for the other?
Ben's user avatar
  • 3,203
23 votes
3 answers

How can I get a significant overall ANOVA but no significant pairwise differences with Tukey's procedure?

I performed with R an ANOVA and I got significant differences. However when checking which pairs were significantly different using the Tukey's procedure I did not get any of them. How can this be ...
L_T's user avatar
  • 1,713
7 votes
3 answers

Why does $\mu > 0$ (or even $\mu > \epsilon$) "seem easier” to substantiate than $\mu \neq 0$?

Consider a random variable $X$ following a normal distribution $N(\mu,\sigma^2)$. Suppose that we have drawn iid samples of $X$, obtaining a data set with a sample mean $\bar{x}>0$. We want to test ...
Nuno's user avatar
  • 128
3 votes
2 answers

Relationship of significance level and p-values

In a hypothesis test, the null hypothesis $H_0$ is rejected in favor of $H_1$ if $|\bar X|>\mu$. When tests found that $\bar x$ is the mean of the samples, a p-value is computed using $$ p=\Pr(|\...
wd violet's user avatar
  • 605
9 votes
1 answer

Surprising behavior of the power of Fisher exact test (permutation tests)

I met a paradoxical behavior of so-called "exact tests" or "permutation tests", the prototype of which is Fisher test. Here it is. Imagine you have two groups of 400 individuals (e.g. 400 control vs ...
Elvis's user avatar
  • 12.4k
2 votes
1 answer

Which statistical analysis should I perform if the data sets are not normally distributed?

I am doing an experiment where there are two independent groups; one is the group of "infected" patients another is the group of "sepsis" patients. I am comparing "platelet monocyte aggregates(PMA)" ...
Saurabh Goswami's user avatar
2 votes
1 answer

R Tukey HSD Anova: Anova significant, Tukey not? [duplicate]

i created a simple anova with three groups in R and get a significant Result. After that i do a Tukey HSD Test and now nothing is significant. How can that be? Pr(>F): 0.0316 Group | p adj 1 - 2 ...
Robinator's user avatar