1. ABSITE statistics: the absolute basics
Christian Jones, MD, FACS
Department of Surgery
Johns Hopkins School of Medicine

2. stats mean: typical “average” median: middle number
mode: most frequent number
normal: type of distribution, equal about a mean, “bell curve”, mean = median = mode

3. terms
incidence: interval of time
prevalence: point in time

4. types of studies
cohort study: prospective, nonrandom assignment to treatment group
case-control study: retrospective, nonrandom

5. biases
selection bias: test groups end up being different, e.g., volunteers vs. population
measurement bias: aka system bias, actual measurement is inaccurate, e.g., recall bias
exposure bias: aka treatment bias, treatments not applied equally or as originally planned, e.g., dead patients “withdraw”

6. test parameters sensitivity: how well does the test see the disease?
specificity: how well does the test make sure it really is the disease?
positive predictive value: if the test says yes, how certain can you be that it’s right?
negative predictive value: if the test says no, how certain can you be that it’s right?

7. copyright, etc.
This document is entirely the work of Christian Jones and is hereby released into the public domain, with no rights reserved. This is version 1.1, last modified on 28 January 2016 by Christian Jones. Contact the author by or on Twitter for questions, comments, or concerns.