Compare the average of two independent groups from their summary statistics. This uses Welch’s t-test, which is more reliable than the classic version when the two groups have different variances.
How to use it
Enter the mean, standard deviation and sample size for each group. You do not need the raw data — the summary numbers from your descriptive statistics are enough.
How to read the result
A p-value below 0.05 means the difference between the two group means is statistically significant at the usual level. The calculator also gives Cohen’s d, which tells you how large the difference is, not just whether it is significant.
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Frequently asked questions
When should I use a t-test?
Use an independent-samples t-test to compare the means of two separate groups on a numeric outcome — for example, test scores of a treatment group versus a control group. For three or more groups, use ANOVA instead.
What if my data are not normally distributed?
For small, skewed samples the Mann-Whitney U test is a safer choice. Our Mann-Whitney calculator handles that case from your raw values.
What does Cohen’s d tell me?
It is the standardised size of the difference: roughly 0.2 is small, 0.5 medium and 0.8 large. Reporting it alongside the p-value shows whether a significant result is also practically meaningful.