Paired t-Test

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Example: eight people were weighed before and after three months of dieting. Did their weight really drop, or could the difference be chance? Change the values to work out your own case.

Before One value per person, separated by spaces or commas. After In the same order as the people before.

Step by step

What each term means

t Statistic: How many standard errors the mean change is from zero. Compared with the t distribution with n − 1 degrees of freedom, it gives the p-value.
Mean Difference (d̄): The mean of each person's after − before difference. Everyone is compared with themselves, so differences between people drop out.
Standard Error (s_d / √n): How much the mean difference varies from sample to sample: the standard deviation of the differences divided by the root of the number of pairs.

When to use it, assumptions and alternatives: the paired t-test in the statistical tests catalog.