For within group changes the SRM is used. However, the sample size takes in account the ES. In a study of Health Related Functional Status that intends to assess within group changes over time with a ratio scale, how can I calculate the sample size?
Hi Gordon. Thank you for your answer.
How is the way to calculate the sample size in a one group study that intends to measure the health status by comparing post vs. pre intervention estimate?
To calculate the sample size, the Effect Size is used. However I read that the Effect Size is used when you compare two groups (which is not the case I would assess). Besides, to assess a Minimally Clinically Important Difference, the Standardized Response Mean has been used for one group studies, and I understand that it is used rather than the Effect Size.
However, I have not found clearly if I need to use the Effect Size or the Standardized Response Mean to calculate a one group study that intends to measure the post vs pre intervention difference.
I really appreciate any ideas on that question.
Mario.
Number of dependent measures (variables) times 10 (or: N = #DV x 10)
So if you have 6 dependent measures, you need at least 60 participants....
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