used more than 45 million times!

Below you will find descriptions and links to 24 free statistics calculators for computing probability values (p-values).

If you like, you may also use the search page to help you find what you need.

This calculator will compute the probability of an individual binomial outcome (i.e., a binomial probability), given the number of successes, the number of trials, and the probability of a successful outcome occurring.

This calculator will compute the probability that event A will not occur (i.e., the complementary probability of A), given the probability of event A occurring.

This calculator will compute the probability of event A occurring, given that event B has occurred (i.e., the conditional probability of A), given the joint probability of events A and B, and the probability of event B.

This calculator will tell you the cumulative area under the standard normal distribution, given a z-score (i.e., the cumulative probability from minus infinity to the z-score).

This calculator will compute cumulative probabilities for a binomial outcome, given the number of successes, the number of trials, and the probability of a successful outcome occurring. For the number of successes x, the calculator will return P(X<x), P(X≤x), P(X>x), and P(X≥x).

This calculator will compute cumulative probabilities for a Poisson outcome, given the total number of events observed, the expected number of events per interval, and the total number of intervals. For the total number of events observed *k*, the calculator will return P(K<k), P(K≤k), P(K>k), and P(K≥k).

This calculator will tell you the Fisher F-value for a multiple regression study and its associated probability level (p-value), given the model R^{2}, the number of predictors in the model, and the total sample size.

This calculator will compute both the exact hypergeometric probability and the exact two-tailed probability of obtaining a distribution of values in a 2x2 contingency table using Fisher's exact test, given the number of observations in each cell.

This calculator uses the Freeman-Halton extension of Fisher's exact test to compute the (two-tailed) probability of obtaining a distribution of values in a 2x3 contingency table, given the number of observations in each cell.

This calculator uses the Freeman-Halton extension of Fisher's exact test to compute the (two-tailed) probability of obtaining a distribution of values in a 3x3 contingency table, given the number of observations in each cell.

This calculator will compute the probability of a specified interval under a (continuous) uniform distribution, given the values of the upper and lower boundaries of the distribution and the values of the upper and lower boundaries of the probability interval.

This calculator will compute the probability of two events A and B occurring together (i.e., the joint probability of A and B), given the conditional probability of event A, and the probability of event B.

This calculator will tell you the one-tailed (right-tail) area under the standard normal curve, given a Z-score (i.e., the one-tailed probability from the z-score to positive infinity).

This calculator will tell you the one-tailed (right-tail) probability value for a chi-square test (i.e., the area under the chi-square distribution from the chi-square value to positive infinity), given the chi-square value and the degrees of freedom.

This calculator will tell you the one-tailed and two-tailed probability values of a t-test, given the t-value and the degrees of freedom.

This calculator will tell you the probability level (p-value) for an analysis of variance (ANOVA) study, given the ANOVA study's between and within groups degrees of freedom and associated F-value.

This calculator will tell you the probability value of an F-test, given the F-value, numerator degrees of freedom, and denominator degrees of freedom.

This calculator will tell you the significance (both one-tailed and two-tailed probability values) of a Pearson correlation coefficient, given the correlation value r, and the sample size.

This calculator will compute a Poisson probability (i.e., the probability of a specific number of events occurring within a specific number of fixed intervals of time or space), given the total number of events observed, the expected number of events per interval, and the total number of intervals.

This calculator will determine whether two correlation coefficients are significantly different from each other, given the two correlation coefficients and their associated sample sizes. Values returned from the calculator include the probability value and the z-score for the significance test. A probability value of less than 0.05 indicates that the two correlation coefficients are significantly different from each other.

This calculator will determine whether the slopes of two lines are significantly different from each other, given the slope, standard error, and sample size for each line. Values returned from the calculator include the probability value, the t-value for the significance test, and the degrees of freedom. A probability value of less than 0.05 indicates that the two slopes are significantly different from each other.

This calculator uses the Sobel test to tell you whether a mediator variable significantly carries the influence of an independent variable to a dependent variable; i.e., whether the indirect effect of the independent variable on the dependent variable through the mediator variable is significant. This calculator returns the Sobel test statistic, and both one-tailed and two-tailed probability values.

This calculator will tell you the two-tailed area under the standard normal curve, given a Z-score (i.e., the two-tailed probability from +/- the Z-score to infinity on both tails of the distribution).

This calculator will compute the probability of event A or event B occurring (i.e., the union probability for A and B), given the probability of event A, the probability of event B, and the joint probability of events A and B.