For the Czech national bioinformatics conference (ENBIK) I prepared a short presentation on Type S and Type M errors and how to use simulations to understand what your method might do before conducting an experiment. I show how t-test can fail, inspired by Andrew Gelman’s take on power = .06 and how DESeq2 (used to determine differentially expressed genes) does a good job at mitigating false positives at the cost of increased false negatives.