For those of you who are Gerd Gigerenzer fans (and who isn't these days), here's an exercise for the reader involving a new screening test for Alzheimer's. Actually, feeling that one never knows when it will strike, it's just a cheap trick to get you to check my own calculations.
There's a new BMJ report of a self-administered test for Alzheimer's. Takes only 5 minutes. The authors conclude "It is a powerful and valid screening test for the detection of Alzheimer's disease". Wow! They report sensitivity of 93% [probability of correctly detecting Alzheimer's] and specificity of 86% [probability of correctly rejecting diagnosis of Alzheimer's]. An accompanying editorial helpfully notes that the prevalence of dementia [which would mostly be Alzheimer's] is 13 per 1000 in people aged 65-69. Questions: 1) Using this "powerful" test, for every patient correctly identified as having Alzheimer's, how many patients will be incorrectly so identified with this devastating diagnosis? 2) Do you think this test is as useful as the authors claim? The first person to correctly respond will receive a free orientation to time and place. Sources: Article: Brown, J. et al (2009). Self administered cognitive screening test (TYM) for detection of Alzheimer's disease: cross sectional study. BMJ, 338: b 2030 [on-line first] Free at http://www.bmj.com/cgi/reprint/338/jun08_3/b2030 Editorial: Nicholl, C. (2009). Diagnosis of dementia. BMJ 338: b1176. You get a sufficient peek at it, plus, despite its warning that payment is required, free access to the rest when you click on "full text of this article" at http://www.bmj.com/cgi/content/extract/338/jun08_3/b1176?papetoc Stephen ----------------------------------------------------------------- Stephen L. Black, Ph.D. Professor of Psychology, Emeritus Bishop's University e-mail: [email protected] 2600 College St. Sherbrooke QC J1M 1Z7 Canada Subscribe to discussion list (TIPS) for the teaching of psychology at http://flightline.highline.edu/sfrantz/tips/ ----------------------------------------------------------------------- --- To make changes to your subscription contact: Bill Southerly ([email protected])
