Hey @ReneBt. Baseline conversion rate is the percentage of visitors to your website that complete a desired goal that you are observing without changing anything. In other words the conversion rate of the control group. For the different values you are getting, did you select "Relative". The default is "Absolute".

Good answer! Think about this way: A random variable has a distribution. It can be skweded to the left, to the right. I can be bi-modal etc. By reducing the variable to it's mean value you are removing all that extra information (uncertainty) and replacing a distribution (intervals) by a single point estimate.

I just realized that the approach is not feasible as I have to estimate $F(X)$ for 3650 values of $X$ and also calculate the credibility interval for each value of $X$. That will take way to long considering the time it already takes to simulate the posterior of $\alpha$ and $\lambda$. @Xi'an: Can you give me a hint on how to infer the posterior of $F(25)$ from the posterior of $\alpha$ and $\lambda$?

Thanks for your input. Because I have to simulate the posterior using the R package LaplacesDemon I will add the estimation of F(x) for each iteration of $\alpha$ and $\lambda$. That should give me a distribution for the F(x) value from which I can get the credibility interval.