Statistics Calculators
Standard deviation, probability and statistics tools.
About these calculators
Twenty calculators for the statistics course and the analysis desk: distributions evaluated at any point, confidence intervals built properly from sample statistics, hypothesis-test helpers that distinguish tails, and inter-relationship measures from covariance through odds ratio. Formulas follow textbook and software conventions — population versus sample variants flagged wherever they diverge, because using n instead of n−1 silently skews small samples.
Interpretation matters as much as computation. The p-value tool explains what a p-value is and is not; chi-square warns when expected cell counts run low; correlation explicitly does not imply causation. These notes exist because a computed statistic without interpretation is how numbers mislead.
Choosing the right calculator
Describing data
Mean-median-mode summarises centre; variance and standard-deviation quantify spread; percentile locates a value within a distribution; z-score converts between raw scores and standard units with between-percentage areas shown.
Testing and estimating
Confidence-interval builds ranges for means and proportions; sample-size plans studies before collection; critical-value finds cut-offs for chosen significance levels; p-value evaluates observed test statistics; binomial and normal-distribution compute exact and approximate probabilities for count and continuous outcomes.
Relationships and risk
Correlation-coefficient and covariance measure linear association; bayes-theorem updates beliefs with evidence; relative-risk and odds-ratio compare outcomes across groups — the standard toolkit for reading medical and A/B-test claims critically.
Statistics calculators we stand behind
Also available (20) — work in progress, not yet indexed
These calculators work but are still being checked for accuracy and sourcing, so they are not in search yet. They are free to use.