Effective N

[Karoline K.]

Dear FUMA Team

For case control studies, should N be the TOTAL N or the effective N? The total N can misrepresent the sample size of the number of cases and controls is very unequal.

Thanks,

Karoline

[Tanya Phung]

Hi Karoline, 

From the submission page, it was mentioned that TOTAL N (cases + controls) should be used: 

The sample size N is used only in MAGMA analyses. Since I do not support MAGMA, if you have questions regarding the effect of using total sample size vs effective sample size, you can consult the MAGMA manual and/or send a message to the developers of MAGMA. 
MAGMA manual: https://cncr.nl/research/magma/

Best,
Tanya

[Karoline K.]

Very helpful, thank you for the super quick reply! You are right, the manual also mentions the total sample size. 

However, personally I dont think that is the right choice. I will be using the effective sample size and just wanted to mention this here in case others have a similar question. 

Best wishes

Karoline 

The N and ncol modifiers are used to specify the sample size. The N modifier is used to specify
the sample size directly (the total sample size, also when using case-control analysis results).The N and ncol modifiers are used to specify the sample size. The N modifier is used to specify
the sample size directly (the total sample size, also when using case-control analysis results).