Comparing 2 Proportions: Power Calculation Results - Quick Tab

Calculating Power

Select the Quick tab of the Comparing 2 Proportions: Power Calculation Results dialog box to access options to interactively view the results of power calculations and generate plots of power as a function of quantities that affect power 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 Power Charts.

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

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

Start Pi1. In the Start Pi1 box, the starting value of Pi1 used in the Power vs. Pi1 power chart.

End Pi1. In the End Pi1 box, enter the final value of Pi1 used in the Power vs. Pi1 power chart.

Start Alpha. In the Start Alpha box, enter the starting value of alpha used in the Power vs. Alpha power chart.

End Alpha. In the End Alpha box, enter the final value of alpha used in the Power vs. Alpha power chart.

No. of Steps. In the No. of Steps box, enter the number of steps, or intervals, to plot on the X-axis in the power charts specified in the Power Charts group box.

Power Charts. Use the buttons under Power Charts to produce charts of power as a function of values known to affect it. 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.

Power vs. N. Click the Power vs. N button to produce a plot of power versus sample size N, for a two sample Z-statistic where both sample sizes are equal to N.  

Power vs. N1. Click the Power vs. N1 button to produce a plot of power versus group 1 sample size, where the group 2 sample size is held constant at the current fixed parameter value.

Power vs. N2. Click the Power vs. N2 button to produce a plot of power versus group 2 sample size, where the group 1 sample size is held constant at the current fixed parameter value.

Power vs. Pi1. Click the Power vs. Pi1 button to produce a plot of power vs. the population proportion for group 1.

Power vs. Alpha. Click the Power vs. Alpha button to produce a plot of power versus type I error rate.