The simpower ado does a Monte Carlo power simulation of one-way anova designs. Here is how you can download the commands from ATS. You can download the simpower command by typing search simpower (see How can I use the search command to search for programs and get additional help? for more information about using search). Now, let’s looks at several examples using simpower.
Let’s begin by simulating a three group anova using usage #1.
simpower, groups(3) n(5 5 5) mu(10 12 14) s(3 3 3) Sample Sizes, Means and Standard Deviations ------------------------------------------- N1 = 5 MU1 = 10 S1 = 3 N2 = 5 MU2 = 12 S2 = 3 N3 = 5 MU3 = 14 S3 = 3 1000 simulated ANOVA F tests ------------------------------ Alpha Simulated Level Power ------------------------------ 0.1000 0.5260 0.0750 0.4680 0.0500 0.3820 0.0250 0.2600 0.0100 0.1440 simpower, groups(3) n(10 10 10) mu(10 12 14) s(3 3 3) Sample Sizes, Means and Standard Deviations ------------------------------------------- N1 = 10 MU1 = 10 S1 = 3 N2 = 10 MU2 = 12 S2 = 3 N3 = 10 MU3 = 14 S3 = 3 1000 simulated ANOVA F tests ------------------------------ Alpha Simulated Level Power ------------------------------ 0.1000 0.8330 0.0750 0.7800 0.0500 0.7110 0.0250 0.5900 0.0100 0.4440
Next, we will use simpower beginning with a real anova (usage #2).
use https://stats.idre.ucla.edu/stat/stata/ado/analysis/crf33
anova y b
Number of obs = 45 R-squared = 0.2957
Root MSE = 9.35626 Adj R-squared = 0.2621
Source | Partial SS df MS F Prob > F
-----------+----------------------------------------------------
Model | 1543.33333 2 771.666667 8.82 0.0006
|
b | 1543.33333 2 771.666667 8.82 0.0006
|
Residual | 3676.66667 42 87.5396825
-----------+----------------------------------------------------
Total | 5220.00 44 118.636364
simpower y b
Sample Sizes, Means and Standard Deviations
-------------------------------------------
N1 = 15 MU1 = 27.666666 S1 = 8.7722502
N2 = 15 MU2 = 35.333332 S2 = 7.8437114
N3 = 15 MU3 = 42 S3 = 11.141941
Results of Standard ANOVA
----------------------------------------------------------------------
Dependent Variable is y and Independent Variable is b
F( 2, 42.00) = 8.815, p= 0.0006
----------------------------------------------------------------------
1000 simulated ANOVA F tests
------------------------------
Alpha Simulated
Level Power
------------------------------
0.1000 0.9730
0.0750 0.9580
0.0500 0.9350
0.0250 0.8840
0.0100 0.8260