t test calculator
Compare two means from summary statistics, or one mean against a hypothesized value. Runs in your browser.
p is not below alpha 0.05.
Questions
Welch or Student t test?
Welch's t test does not assume the two groups have equal variances and adjusts the degrees of freedom. Student's t test pools the SDs and assumes equal variance. Welch is the safer default.
What does the p-value mean?
The p-value is the probability of a difference at least this large if the true difference were zero. It is not the probability that the hypothesis is true.
What is the 95% confidence interval?
It is a range for the mean difference built from the standard error and the t critical value. Intervals built this way cover the true difference 95% of the time over repeated studies.
Educational only. Not medical advice, not a regulatory determination, and not a substitute for qualified RA/QA, legal, clinical, or statistical counsel. t test calculator does not submit to FDA, Notified Bodies, or IRBs. This is research arithmetic, not a clinical test and not a diagnosis.