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Significance calculator
t-test, Mann-Whitney, correlation, chi-square with a results sentence
What does it mean?
p is the probability of seeing a result at least this clear if there is really no difference or relationship. Below 0.05 counts as significant. The effect size says how large the difference is — always report it.
Learn more
- Testing for normalityCheck normality with a histogram or Q-Q plot, skewness and kurtosis, and the Shapiro-Wilk test. With large samples, plots matter more than p-values.
- p-value and significanceThe p-value is the probability of a result at least as extreme as yours if the null hypothesis were true. p < .05 is usually called significant.
- Effect sizeAn effect size tells you how large a difference or relationship is, independent of sample size. Cohen’s d of 0.2, 0.5 and 0.8 is small, medium, large.
- Confidence intervalA 95% confidence interval gives a range of plausible values for a population parameter. It shows both the size of an estimate and its precision.
- t-testA t-test checks whether two means differ significantly: two independent groups, two paired measurements, or one mean against a fixed value.
- Chi-square testThe chi-square test checks whether two categorical variables are related (independence) or whether frequencies match an expected distribution.
