power

Power calculations

Posted on May 3, 2021May 3, 2021 by LV

Underpowered studies are a big (but far from the only) source of the current replication crisis in the medical literature. Power calculations hinge on the expected effect size (often expressed as Cohen’s d), the populations’ spread around the mean (standard deviation) and arbitrary frequentist assumptions about alpha and beta. Cohen’s d is conceptually similar to…

The Reproducibility Crisis in Medicine

Posted on April 30, 2021May 5, 2021 by LV

In 2005, Stanford epidemiologist John Ioannidis published the provocatively titled paper “Why most published research findings are false” (Ioannidis, PLoS Med 2005, 2:e12), that has since become a foundational piece of metascience. Among other things, he stated: The smaller the study sample conducted in a scientific field, the less likely the research findings are to…