Slightly different outcomes everytime I execute the same analysis
Currently, I am writing my Masterthesis in the faculty of Human Factors & Engineering Psychology. For my data analysis I am using JASP in order to execute a bayesian repeated measures anova. However, I got the problem, that everytime I execute the analysis anew with exactly the same data, I receive slightly different outcome values e.g. for the bayes factor or credible interval. I do not have an explanation for this. Is this usual?
Moreover, my bayes factor and credible interval values of main effect also change when I add a covariate. This has huge consequences for the main effects found, as somehow there occurs an effect but merely when no covariate is added. But again, I do not know why that is the case.
Another question I have also concerns the model averaged posterior summary. How is the mean and standard deviation built here, as these are not the actual means or SD`s of the scores. Is there a certain distribution when bayesian statistics is applied? I could not find that information in the student guide, unfortunately.
I would really appreciate, if you could help me with this problem.