Statistics & Probability Calculators
From averages to p-values — descriptive stats, probability and inference made simple.
Updated June 2026 · Free · No sign-up
This cluster covers the full path from raw data to a conclusion, useful for students, researchers and analysts alike. Begin with descriptive statistics — the Average and Mean/Median/Mode calculators summarise central tendency, while the Standard Deviation and Descriptive Statistics calculators add variance, quartiles, IQR and skewness so you can see how spread out and shaped your data is.
From there, the inference tools help you test ideas and plan studies. The Z-Score calculator places a value on the normal distribution and finds its percentile, the Confidence Interval and P-Value calculators support hypothesis testing at any confidence level, and the Sample Size calculator tells you how many responses a survey needs for a target margin of error. For counting problems, the Permutation & Combination and Probability calculators handle nPr, nCr and event likelihoods — with step-by-step working so you can learn the method, not just the answer.
All Statistics & Probability Calculators
Std Deviation Calculator
Calculate standard deviation, variance, and summary statistics from a dataset.
Average Calculator
Calculate mean, median, mode, and range from any list of numbers.
Mean/Median/Mode Calculator
Calculate mean, median, mode, and range from any dataset with step-by-step solution.
Z-Score Calculator
Calculate z-score, standard score, and find what percentile a value falls in on the normal distribution.
Confidence Interval Calculator
Calculate confidence intervals for a population mean with any confidence level.
P-Value Calculator
Calculate p-value from a z-score or t-statistic for one-tailed and two-tailed hypothesis tests.
Sample Size Calculator
Calculate required sample size for surveys and experiments at any confidence level and margin of error.
Permutation & Combo Calculator
Calculate nPr permutations and nCr combinations for any n and r values.
Probability Calculator
Calculate probability of events, combinations, and permutations.
Descriptive Statistics Calculator
Calculate mean, median, mode, quartiles, IQR, variance, standard deviation, and skewness.
Percent Error Calculator
Calculate percent error between experimental and theoretical values in science experiments.
Frequently asked questions
What is the difference between mean, median and mode?
The mean is the arithmetic average (sum divided by count), the median is the middle value when the data is sorted, and the mode is the value that appears most often. The median is more robust to outliers and skew, so it often describes incomes or house prices better than the mean. A dataset can have one mode, several modes or none at all.
What does a p-value actually tell me?
A p-value is the probability of seeing a result at least as extreme as yours if the null hypothesis were true. A small p-value (commonly below 0.05) suggests the data is unlikely under the null hypothesis, so the result is often called statistically significant. It does not measure the size or real-world importance of an effect, nor the probability that your hypothesis is correct.
How do I choose a sample size for a survey?
Sample size depends on your chosen confidence level (often 95%), your acceptable margin of error, and the expected variability in responses; for a large population the result barely changes with population size. Tightening the margin of error or raising the confidence level both increase the required sample. The Sample Size calculator works these out, and you usually round up to ensure the margin is met.
What is the difference between population and sample standard deviation?
Population standard deviation divides by N and is used when your data covers the entire group of interest, while sample standard deviation divides by n−1 (Bessel's correction) when your data is a sample meant to estimate a larger population. The n−1 adjustment corrects the tendency of a sample to understate the true variability. For large datasets the two values are very close, but for small samples the difference is meaningful.
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