Statistics
Distributions, hypothesis tests, and confidence intervals for any dataset.
44 tools
Standard Deviation
Mean, variance, and SD for any dataset.
P-Value Calculator
From a test statistic and distribution.
Confidence Interval
For a mean or proportion.
Z-Score Calculator
Standardize a value and find its percentile.
Normal Distribution
Probabilities under the bell curve.
T-Test Calculator
One- and two-sample tests with p-value.
Chi-Square Calculator
Goodness-of-fit from observed vs expected.
Correlation Calculator
Pearson's r, r², and significance.
Sample Size Calculator
Participants needed for a margin of error.
ANOVA Calculator
One-way analysis of variance, F-table.
Mean, Median, Mode
Mean, median, mode, range, and quartiles from a data set.
Linear Regression
Least-squares line, slope, intercept, and r².
Percentile Calculator
Percentile rank of a value, and value at a percentile.
Binomial & Poisson
Binomial and Poisson probabilities.
Probability Calculator
Single and combined event probabilities.
Effect Size Calculator
Cohen’s d effect size from two group means and standard deviations.
Margin of Error Calculator
Margin of error for a survey proportion at a confidence level.
Five-Number Summary
Min, Q1, median, Q3, max, IQR, and outliers with a box plot.
Weighted Mean Calculator
Weighted average from value and weight pairs.
Geometric Mean Calculator
Geometric mean of a set of positive numbers.
Coefficient of Variation
Relative variability — standard deviation as a percent of the mean.
Test Item Analysis
Difficulty, discrimination, point-biserial, and KR-20 from a response matrix.
Cronbach’s Alpha
Scale reliability from item variances or the average inter-item correlation.
Split-Half Reliability
Correct a half-test correlation up to full length with Spearman-Brown.
Cohen’s Kappa
Chance-corrected agreement between two raters on a 2×2 table.
Fleiss’ Kappa
Agreement across three or more raters and any number of categories.
Intraclass Correlation
Single-rater and average-rater ICC from an ANOVA mean-square table.
Mann-Whitney U Test
Nonparametric comparison of two independent groups, with U, z, and p.
Wilcoxon Signed-Rank
Nonparametric test for paired data, with W, z, p, and effect size.
Kruskal-Wallis Test
Nonparametric ANOVA across three or more groups, with H and p.
McNemar’s Test
Test a change in paired yes/no data, with the exact binomial alternative.
Odds Ratio & Risk Ratio
Odds ratio and risk ratio from a 2×2 table, with confidence intervals.
Sensitivity & Specificity
Diagnostic accuracy from TP, FP, FN, and TN, with likelihood ratios.
APA Results Formatter
Format a t, F, χ², or r result in APA 7 style, ready to paste.
Bayes’ Theorem
Update a probability with evidence, with the frequency table.
Expected Value
E(X) for a discrete distribution, with variance and SD.
Standard Error
SE of a mean or proportion, with margin and interval.
Power Analysis
Participants needed for a target power, or the power you already have.
Bootstrap Intervals
Resampling intervals for the median and other formula-free statistics.
Logistic Regression
Fit a binary outcome, with odds ratios and their confidence intervals.
Tukey HSD
Every pairwise comparison after an ANOVA, with adjusted p-values.
Levene’s Test
Test whether groups have equal spread, before an ANOVA or t-test.
Shapiro–Wilk Test
Test a sample for normality, with the Q–Q plot alongside.
Critical Value Calculator
Critical values for z, t, χ² and F from α and degrees of freedom.
About statistics tools
Compute the statistic, see the distribution, and understand what the number means — not just what it is.
When to use these tools
Common statistics tasks and the tool that handles each one.
Frequently asked questions
Common questions about statistics — the concepts behind the tools above.