GlenCalc

t-test calculator

A t-test asks whether a mean differs from a value, or two means differ from each other, by more than chance would explain.

Your answer

p-value0.0782Not significant at α = 5%
t statistic1.8257
Degrees of freedom29
Standard error2.7386
Critical t2.0452

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How we worked it out

Updated as you change the numbers.

  1. SE = s ÷ √n. t = (x̄ − μ₀) ÷ SE, with n − 1 degrees of freedom.

Method and assumptions

The p-value is the chance of a t statistic at least this extreme if there were truly no difference. Welch’s test does not assume the two groups have equal variances, which makes it the safer default.

Questions

Is a sample mean of 105 (SD 15, n = 30) different from 100?

Not at the 5% level: t = 1.826 with 29 degrees of freedom, two-tailed p = 0.078.

Sources

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