Tests & Inference
Z-scores, confidence intervals, sample size, t-tests and chi-square.
- Chi-Square Goodness of Fit Calculator Tests whether observed counts match the expected proportions.
- Chi-Square Test of Independence Calculator A chi-square test on a table of counts, with the expected counts and effect size.
- Cohen’s d Calculator The effect size between two groups, as Cohen’s d and Hedges’ g.
- Confidence Interval Calculator A confidence interval for a mean, from the sample mean, standard deviation and size.
- Confidence Interval for a Proportion Calculator A confidence interval for a percentage, by the Wilson and the simple normal (Wald) methods.
- Margin of Error Calculator The margin of error of a survey result from its sample size and confidence level.
- One-Way ANOVA Calculator A one-way analysis of variance across up to six groups, from your raw data.
- P-Value Calculator The p-value from a z, t, chi-square or F statistic.
- Proportion Z-Test Calculator A z-test for one proportion against a value, or for the difference between two proportions.
- Sample Size Calculator How many responses a survey needs for a given margin of error and confidence level.
- Sample Size for a Mean Calculator How many measurements are needed to estimate an average to a chosen precision.
- Standard Error Calculator The standard error of a mean or of a proportion.
- Statistical Power Calculator The power of a two-group t-test, and the group size needed to reach a target power.
- T-Score and Critical Value Calculator Student’s t statistic from a sample, with the critical t value for your confidence level.
- T-Test Calculator One-sample, paired and two-sample t-tests from your raw data.
- Two-Sample T-Test from Means and Standard Deviations A two-sample t-test when you only have the means, standard deviations and group sizes.
- Z-Score Calculator How many standard deviations a value is from the mean, and the share of a normal distribution below it.
- Z-Test Calculator A one-sample z-test for a mean when the population’s standard deviation is known.