is the design correct ?

Dear stat friends,

I have a question regarding a design.

The problem is to find significant predictor variables which
have an effect in the apparition of desease.

The problem is that this desease is very rare:it is an affection of the eye
which affect only 20/10000 people.

There are currently around 10 variables that we expect to have an effect.

We have collected in an hospital all the patient files corresponding to the
desease (around 50 cases).

In order to perform a test we need also to have normal people.
We have randomly collected the same number of patient files
which don't have the desease (around 50).

Is it a good design in order to perform a discriminant analysis between
the two groups, or is it better to respect the proportion of the desease
and thus to collect 500*50 normal patient ?

thank you for your contribution.

Best regards,


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