Statistics

Statistics calculators summarize data and test results without a spreadsheet. Start with the average calculator or the mean, median, mode and range calculator for a quick summary, and the standard deviation calculator to measure spread, with a choice of sample or population.

For inference, the z-score calculator standardizes a value, the p-value calculator turns a z-score into a one- or two-tailed p-value, and the confidence interval calculator builds a range around a mean. The sample size calculator estimates how many survey responses you need for a chosen confidence level and margin of error. The probability and statistics calculators round out the group.

Each page explains the formula and when it applies. Most assume random sampling and, for z-based methods, an approximately normal distribution. Check those conditions before you rely on a result, especially with small or skewed data sets.