# Independent Sample t-Test: Power Calculation Results - Quick Tab

Calculating Power

Select the Quick tab of the Independent Sample t-Test: 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 to use in the Power vs. N  power chart.

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

Start Es. In the Start Es box, enter the starting value of Es to use in the Power vs. Es power chart.

End Es. In the End Es box, enter the final value of Es to use in the Power vs. Es power chart.

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

End Alpha. In the End Alpha box, enter the final value of Alpha to use 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 frame.

Power Charts. Click the buttons under Power Charts to produce charts of power as a function of sample size, standardized effect size, or Type I error rate. Note that parameters given under X-Axis Graphing Parameters 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 a plot of power versus sample size N, for an independent sample t-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 (N1), where the Group 2 sample size (N2) 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 (N2), where the Group 1 sample size (N1) is held constant at the current fixed parameter value.

Power vs. Es. Click the Power vs. Es button to produce a plot of power versus standardized effect size (Es).

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