Calculating Required Sample Size

Select the Quick
tab of the Single Proportion: Sample Size Calculation
Results dialog box to access options to interactively view the results
of sample size calculations and generate plots of required sample size
as a function of quantities that affect sample size in practice.

X-Axis Graphing Parameters. The entries in the boxes under X-Axis Graphing Parameters establish the start value, end value, and number of steps on the X-axis for the graphs specified under Sample Size Charts.

Start Pi. In the Start Pi box, enter the starting value of Pi used in the N vs. Pi sample size chart.

End Pi. In the End Pi box, enter the final value of Pi used in the N vs. Pi sample size chart.

Start Alpha. In the Start Alpha box, enter the starting value of alpha used in the N vs. Alpha sample size chart.

End Alpha. In the End Alpha box, enter the final value of alpha used in the N vs. Alpha sample size chart.

Start Power. In the Start Power box, enter the starting value of power goal used in the N vs. Power sample size chart.

End Power. In
the End
Power box, enter the final value of power goal used
in the N vs. Power

No. of Steps.

Algorithm. In the Power Analysis module, you can choose from two algorithms:

Exact. Select the Exact option button to use the binomial distribution to calculate the exact probability of rejecting the null hypothesis, using the standard rejection points (obtained from a normal approximation) used in the test.

Approximate. Select the Approximate option button to use the normal approximation to the binomial distribution to calculate the approximate probability of rejecting the null hypothesis.

Sample Size Charts. Use the buttons in the Sample Size Charts group box to produce charts of required N as a function of power goal, population proportion, or type I error rate. Note that parameters given in the X-Axis Graphing Parameters group box control the range of values plotted on the X-axis and the number of steps plotted.

N vs. Pi. Click the N vs. Pi button to produce a plot of sample size vs. Pi.

N vs. Power. Click the N vs. Power button to produce a plot of sample size (N) versus power goal.

N vs. Alpha. Click the N vs. Alpha button to produce a plot of sample size (N) vs. type I error rate.