# Need to set a specific prior based on base rate information?

I am trying to find the probability of certain symptoms based on group membership (healthy controls vs. people with a particular disease). I used a default Cauchy prior of 0.707.

It then occurred to me that perhaps I need to use base rate information of the disease.

However, I am not sure if this would be appropriate, and if so, how I would input this information into JASP. There might be separate base rate information for a particular symptom or of the disease itself (prevalence?) - which should I use? And how do I translate this into a prior? If no base rate information is present, do I just use the default?

I'm not sure if I'm conceptualizing this correctly or if the default prior I used initially is alright. I'd appreciate any help. Thanks.

## Comments

It appears to me as if you wish to do a comparison of two multinomials. There is one multinomial per group, and each multinomial has the disease categories. So it looks as if you need the contingency table functionality.

Cheers,

E.J.