Better to be 1:2

Dear Amir,

I suggest you to see links and attached files in subject.

-Case-Control Studies - SPH

sphweb.bumc.bu.edu/...Case-Control/EP713_Case-Control_print.ht...

-Case-control study Flashcards | Quizlet

https://quizlet.com/16214330/case-control-study-flash-cards/

-6.5 - Case-Control Study Design | STAT 507

https://onlinecourses.science.psu.edu/stat507/node/48

-Measuring Association in Case-Control Studies

sphweb.bumc.bu.edu/otlt/MPH.../EP/.../EP713_Association8.html

Best regards

A study in which a group of persons with a disease (cases) and a comparison group of persons without the disease (controls) are compared with respect to the history of past exposures to factors of interest.

A study in which a group of persons exposed to a factor of interest and a group of persons not exposed are followed and compared with respect to the incidence rate of the disease or other condition of interest.

The proportion could be determined by calculating the mean of the parameters studied in the cases and in the control group until the mean remains steady. At that point you can calculate the proportion otherwise the proportion cannot be be predetermined because it is subject to factors inherent in the particular case-control study.

I think better be matched

1:1

1:2

But you need to use sample calculation formula tht take in consideration the case:control ratio

1:3 is the best n case control study