# Setting subjective beta priors in JASP?

Hi everyone,

I have been wondering how to calculate the distribution width which to input for the subjective priors in JASP?

I found how to produce the beta distribution plot in R but what do I enter into JASP?

If I was using the ice cream/weather example for prior calculation from this blog

https://towardsdatascience.com/probability-concepts-explained-bayesian-inference-for-parameter-estimation-90e8930e5348

Could I do it as follows?

There are 10 studies who have measured mood over Antarctic winter using the same tool as I am using for Arctic winter.

9 of the 10 studies have shown that mood is worst in the winter.

Does this mean my prior would be 0.9?

Kind regards,

eniseg

## Comments

Are you using a binomial model, and do you want to use a beta prior? You can set the "a" and "b" parameters of the prior distribution. If you start from a uniform distribution (big if) then, after seeing 9/10 "successes", you have a = 10 (i.e., 9+1) and b = 2 (i.e., 1+1) to define the prior when awaiting the 11th outcome. https://en.wikipedia.org/wiki/Conjugate_prior

E.J.