In this initial example, you would like to design an experiment that has 90% power to detect a difference of 1.5 seconds at a significance level of α = 0.05. Use the One Sample Mean calculator to calculate the number of samples you need to test.
1.
Select DOE > Design Diagnostics > Sample Size and Power.
2.
Click the One Sample Mean button.
3.
Leave Alpha set to 0.05.
4.
Enter 2 for Std Dev.
5.
Leave Extra Parameters set to 0.
6.
Enter 1.5 for Difference to detect.
7.
Leave Sample Size blank.
8.
9.
Click Continue.
Figure 16.4 One-Sample Mean Calculator
1.
Select DOE > Design Diagnostics > Sample Size and Power.
2.
Click One Sample Mean.
3.
Leave Alpha set to 0.05.
4.
Enter 2 for Std Dev.
5.
Leave Extra Parameters set to 0.
6.
Enter 1.5 for the Difference to detect.
7.
Leave Sample Size blank.
8.
Leave Power blank.
9.
Click Continue to launch the power by sample size plot.
Figure 16.5 Power by Sample Size
1.
Select DOE > Design Diagnostics > Sample Size and Power.
2.
Click One Sample Mean.
3.
Leave Alpha set to 0.05.
4.
Enter 2 for Std Dev.
5.
Leave Extra Parameters set to 0.
6.
Leave Difference to detect blank.
7.
Enter 21 for Sample Size.
8.
Leave Power blank.
9.
Click Continue.
Figure 16.6 Plot of Power by Difference to Detect for a Sample Size of 21
1.
Select DOE > Design Diagnostics > Sample Size and Power.
2.
Click One Sample Mean.
3.
Leave Alpha set to 0.05.
4.
Enter 2 for Std Dev.
5.
Leave Extra Parameters set to 0.
6.
Enter 1.5 as Difference to detect.
7.
Leave Sample Size blank.
8.
Leave Power blank.
9.
Click Animation Script.
Figure 16.7 Initial Animation Script to Illustrate Power
The red curve shows the t-distribution when the true mean is zero.
The blue curve shows the t-distribution when the true mean is 1.5, which is the difference to be detected.
By default, the animation shows a two sided test. Use the Two Sided, Low Side, and High Side buttons to toggle between not equal, less than, or greater than alternative hypotheses.

Help created on 7/12/2018