Sample size calculation: Single mean
Calculates the required sample size for the comparison of a sample mean with a given value. The sample size takes into account the required significance level and power of the test (see Sampling: Introduction).
In the example you consider a value of at least 60 to be significant different from the null hypothesis value 50. From a previous study, you expect the standard deviation of the sample to be 14.
For α-level you select 0.05 and for β-level you select 0.20 (power is 80%).
After you click the Calculate button the program displays the required sample size, which is 18 in the example.
A table shows the required sample size for different Type I and Type II Error levels.
Comparison of two paired samples
To calculate the sample size required for the comparison of two paired samples, you use the same procedure as for a Single mean.
In the dialog box, for Mean, you enter the hypothesized mean difference; for Standard deviation, enter the hypothesized standard deviation of the differences, and for Null hypothesis value enter the value 0.