To calculate a sample size for a hypothesis test about two proportions, specify the following quantities and test settings in the legacy calculator:
Alpha
The probability of a type I error, which is the probability of rejecting the null hypothesis when it is true. It is commonly referred to as the significance level of the test. The default alpha level is 0.05.
Proportion 1
The proportion for population 1, which could be known or hypothesized. The default value is 0.5.
Proportion 2
The proportion for population 2, which could be known or hypothesized. The default value is 0.1.
One-Sided or Two-Sided
Select either a one-sided or a two-sided test.
Specify two of the following parameters to calculate the third where the sample sizes are considered as one parameter. The sample sizes must both be entered or both be left blank for calculation.
Null Difference in Proportion
The difference in proportions under the null hypothesis. The default value is 0.2.
Sample Size 1
The total number of observations (runs, experimental units, or samples) in the experiment to estimate Proportion 1.
Sample Size 2
The total number of observations (runs, experimental units, or samples) in the experiment to estimate Proportion 2.
Note: When sample size is calculated, Sample Size 1 = Sample Size 2. If you enter sample sizes, they do not have to be equal.
Power
The probability of rejecting the null hypothesis when it is false. High power is desired. With all other parameters fixed, power increases with sample size.
Continue
Evaluates the missing value.
Back
Returns to the previous Sample Size and Power launch window.