Evaluating this function, for a given k and n (and hyperparameters f, a and b) yields a probability P, which we compare to the thresholds 1-PEP and PEP to give the gene an expression call. We used a = 1.5, b = 2, f = 0.2 and PEP = 0.05 to make the calls in this paper, unless otherwise indicated. Thus a gene was considered expressed if it was estimated to be present in at least 20% of the cells with no more than 5% posterior error probability.
