Sample size for repeated measures or dependent-sample t

#1
Hi John:
I have another question. I collected these data from parents and their children about children's chronic condition. I wanted 100 responses, but since I requested the documents from their pharmacy, the response rate was low. I only got 50 parents and 50 children. Since they are related, I suppose I don't need as many as I would for independent samples??? Also, I collected the same variables (not too many) 2 years ago. So, I also want to do a longitudinal analysis. In both cases, would you say that I don't need to have many (well, more the better, but...)? If I did not make myself understood, I am sorry. Please let me know. Thank you.
 

JohnM

TS Contributor
#2
Yes, in general, if you have dependent samples, you can get away with smaller sample sizes because of the higher power of the test design.

50 should be plenty....