Statistics and Probability Reference Library

Calculate standard deviation, variance, and spread with clear statistical outputs.

Convert values to z-scores and estimate probability within a normal model.

Evaluate normalcdf(lower, upper, μ, σ) exactly like a TI-84, with the shaded area and keystrokes shown.

Find the value or z-score for a given area with invNorm(area, μ, σ): left, right, or center tail.

Evaluate binompdf(n, p, k) and binomcdf(n, p, k) like a TI-84, plus a full probability table.

Build a z confidence interval for a population mean at 90%, 95%, or 99% confidence.

Turn raw data into a histogram with a frequency table, relative and cumulative frequencies, and SVG download.

Fit a least-squares line and get the equation, R², coefficient tests, ANOVA table, confidence and prediction intervals, residuals and a plot.

Generate cryptographically secure random integers or decimals in any range, with or without repeats.

Which Statistical Test Should I Use?

Choose the right test in three questions (what you measure, how many groups you compare and whether the data are paired) with a decision table and worked decisions.

Normal Distribution

Explore the bell curve, its properties, and why it appears so often in probability and statistics.

Hypothesis Testing

Learn how null and alternative hypotheses, p-values, confidence intervals, and test selection work together in statistical inference.