Calculator categories, visual statistics tools, and statistical table references for common topics such as descriptive statistics, probability, inference, distributions, and regression.

Are all listed tools interactive?

Some core tools are interactive now, including descriptive statistics, z-scores, normal probabilities, the standard normal table, a bell curve explorer, and a box plot builder. Each listed resource has a dedicated page. Some pages are references; interactive calculations are available where marked.

Does the site save the numbers I enter?

The current calculators run in your browser and do not submit your entered values to a server.

Can I use a result in research or coursework?

Use the tools as learning aids. Check the method, assumptions, and calculations against your course or research requirements before relying on a result.

Are the table values available for every listed reference?

The standard normal table is interactive. Other table entries currently describe the planned references; their numeric values are not yet included.

Notes for curious learners

From the Blog

Short, practical guides to help you choose a method and make sense of statistical results.

↗Choosing a method · 5 min read

How to choose the right statistical test

Start with your question, outcome type, and study design before reaching for a test.

Read article ↓

First identify what you want to learn: compare groups, estimate an association, or test a proportion. Then classify the outcome as numeric, categorical, or ordinal, and note whether observations are independent or paired.

For example, comparing a numeric outcome between two independent groups often points to a two-sample t-test, while paired measurements call for a paired method. For categorical counts, a chi-square test or Fisher's exact test may fit. Check assumptions and sample size before deciding.

?Inference · 4 min read

What does a p-value actually tell you?

A p-value describes how surprising data would be under a specified null model.

Read article ↓

A p-value is the probability, assuming the null hypothesis and model assumptions are true, of observing a result at least as incompatible with the null as the one you saw. It is not the probability that the null hypothesis is true.

Read it alongside the effect estimate, confidence interval, study design, and practical importance. A small p-value can flag a mismatch with the null model, but it does not measure the size or value of an effect.

μDescriptive statistics · 3 min read

Mean or median: which should you use?

Both describe the center, but they react differently to skew and unusual values.

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The mean uses every value and is useful when the distribution is reasonably balanced and the arithmetic average is meaningful. A few extreme observations can pull it away from where most values sit.

The median is the midpoint after sorting and is more resistant to extreme values. For skewed data such as income, report the median with a measure of spread like the interquartile range. A histogram or box plot helps show why one summary may be more informative.