Dear List, I am reading a method and am unsure how to do something similar, so have come here for advice! I have a observed value and a expected value generated from a null model. I am looking to see if observed - expected is significantly different from zero. So in the method in the paper it states: " .. significance of difference from zero was tested with Markov chain Monte Carlo simulation" I have installed the package mcmc as this seemed a good place to start but i am unsure what function to call? I have 600 data points in a data frame called diversity, where the observed value is called, well observed and the expected.. expected! Thanks for any advice. Peter