To calculate a sample size for a hypothesis test about one proportion, 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
The true proportion, which could be known or hypothesized. The default value is 0.1.
Tip: For all other parameters fixed, the largest sample size occurs when the proportion is 0.5.
Method
Select a method. Choices are Exact Agresti-Coull or Exact Clopper-Pearson. The Clopper-Pearson method tends to be more conservative (larger sample size) than the Agresti-Coull method. The exact Agresti-Coull method uses the adjusted Wald-based test statistic.
For more information about the adjusted Wald test statistic, see Agresti and Coull (1998).
For more information about the Clopper-Pearson exact method, see Clopper and Pearson (1934) or Agresti and Coull (1998, Section 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 value, or specify one value to obtain a plot of the relationship between the other two parameters.
Note: The plot uses the normal approximation method rather than an exact method.
Null Proportion
The proportion to test against (p0). The default value is 0.2.
Sample Size
The total number of observations (runs, experimental units, or samples) in the experiment.
Power
The probability of rejecting the null hypothesis when it is false. With all other parameters fixed, power increases as sample size increases.
Continue
Evaluates the missing value when two parameters are specified, or launches a plot comparing two missing parameters if only one parameter is specified.
Back
Returns to the previous Sample Size and Power launch window.