Calculating Required Sample Size

Select the Quick
tab of the Planned
Contrast: 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 Es. In the Start Es box, enter the starting value of Es to use in the N vs. Es sample size chart.

End Es. In the End Es box, enter the final value of Es to use in the N vs. Es sample size chart.

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

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

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

End Power. In the End Power box, enter the final value of the power goal used in the N vs. Power sample size 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 charts specified in the Sample Size Charts group box.

Sample Size Charts. Use the buttons under Sample Size Charts to produce charts of required N as a function of power goal, standardized effect size, 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. Es. Click the N vs. Es. button to produce a plot of N versus standardized effect size .

N vs. Alpha. Click the N vs. Alpha button to produce a plot of N vs. Type I error rate.

N vs. Power. Click the N vs. Power button to produce a plot of N versus power goal.