Test Statistic Calculator

This calculator works out z test statistics with their p-values, critical values and a reject or do-not-reject decision. Choose a one-sample test for a mean, a two-sample test for the difference of two means, both with known population standard deviations, or a test for one proportion or two proportions. Enter the summary figures, the tail and the significance level, and you get the z statistic, standard error and p-value with the formula worked through. If the standard deviation comes from the sample itself, the right statistic is a t, not a z.

Calculator Type

The one-sample z test. Use it only when sigma is genuinely known rather than estimated from the sample; if it came from the sample, the statistic is a t.

Sample Mean *

Hypothesised Population Mean *

Population Standard Deviation (sigma) *

Sample Size (n) *

Tail

Significance Level (%)

Fix this before looking at the data, not after.

Widget

The two-sample z test for independent groups. Like the one-sample version, it needs each group's sigma to be genuinely known; if they come from the samples, use a two-sample t test.

Sample 1 Mean *

Population 1 Standard Deviation (sigma 1) *

Sample 1 Size (n1) *

Sample 2 Mean *

Population 2 Standard Deviation (sigma 2) *

Sample 2 Size (n2) *

Hypothesised Difference (mean 1 - mean 2)

Usually 0, for no difference between the populations.

Tail

Significance Level (%)

Fix this before looking at the data, not after.

Widget