Our World Statistics Day conversations have been a great reminder of how much statistics can inform our lives. Do you have an example of how statistics has made a difference in your life? Share your story with the Community!
Highlighted
agn3284
Level II

Power calculations for categorical variables.

Can someone please explain how JMP calculates statistical power associated with the individual levels and the whole effect of a categorical variable? I know the equations used for calculating power in case of a continuous variable but they don't seem to work in the case of categorical variables.

1 ACCEPTED SOLUTION

Accepted Solutions
Highlighted
julian
Community Manager Community Manager

Re: Power calculations for categorical variables.

Hi agn3284,

It sounds like you're calculating power with DOE > Sample Size and Power > K Sample Means, is that correct? The power calculated there is for the overall, omnibus ANOVA only. Pairwise tests have to be considered separately. Here is a link to some of the technical details for that calculation: Technical Details. Scroll down to "Power for a Categorical Effect."

To calculate power for pairwise companions you would need to use "Two Sample Means" rather than K sample means. Be sure to consider any of the alpha control procedures you'll be using when calculating prospective power.

I hope this helps!

julian

View solution in original post

4 REPLIES 4
Highlighted
julian
Community Manager Community Manager

Re: Power calculations for categorical variables.

Hi agn3284,

It sounds like you're calculating power with DOE > Sample Size and Power > K Sample Means, is that correct? The power calculated there is for the overall, omnibus ANOVA only. Pairwise tests have to be considered separately. Here is a link to some of the technical details for that calculation: Technical Details. Scroll down to "Power for a Categorical Effect."

To calculate power for pairwise companions you would need to use "Two Sample Means" rather than K sample means. Be sure to consider any of the alpha control procedures you'll be using when calculating prospective power.

I hope this helps!

julian

View solution in original post

Highlighted
agn3284
Level II

Re: Power calculations for categorical variables.

Hi Julian,

Thanks for the answer. I created a design using the custom design option consisting of just 1 categorical variable with 3 levels and N = 6 runs. I used the DOE> Evaluate Design option to look at the power values. Will the calculations be the same for those power values?

Highlighted
julian
Community Manager Community Manager

Re: Power calculations for categorical variables.

Hi agn3284,

Yes, that will use the same calculations for power.

julian

Highlighted
agn3284
Level II

Re: Power calculations for categorical variables.

Hi Julian,

The answer was very helpful but I am a little confused on how to get the L matrix. I took the anticipated betas as 1 and -1 for levels 1 and 2 respectively. Can you please explain how to get the L matrix?

Article Labels

    There are no labels assigned to this post.