Monday, July 11, 2011

Re: controlled experiments

Some blog followers might be interested in a discussion-list post “Re: controlled experiments” [Hake (2011)].

The abstract reads:

ABSTRACT: PhysLnrR’s Brian Foley wrote (paraphrasing):

“I would love to be doing controlled experiments much of the time - but they are darn near impossible to pull off. . . . . . Once you have your 40 approved classrooms, you RANDOMLY SELECT 20 TEACHERS and train them on your innovation. . . . . Also your 20 control teachers need to be using their ‘traditional’ teaching (and specifically teach like they have never heard of your innovation. . . . . and if you have designed some good assessments of learning, then you will finally have your result. . . . . .and if your innovation makes a difference YOU JUST MIGHT GET THE MAGICAL p less than 0.05 RESULT.”

Brian seems to have succumbed to the siren calls of the Gold Standardistas and the Statistical Significance Cultists. Modesty forbids mention of these possible antidotes:

a. “Should Randomized Control Trials Be the Gold Standard of Educational Research?” at ,

b. “Seventeen Statements by Gold-Standard Skeptics #2” at ,

c. “The Cult of Statistical Significance” at .

To access the complete 10 kB post please click on .

Richard Hake, Emeritus Professor of Physics, Indiana University Honorary Member, Curmudgeon Lodge of Deventer, The Netherlands
President, PEdants for Definitive Academic References which Recognize the Invention of the Internet (PEDARRII)

“In some quarters, particularly medical ones, the randomized experiment is considered the causal ‘gold standard.’ IT IS CLEARLY NOT THAT IN EDUCATIONAL CONTEXTS, given the difficulties with implementing and maintaining randomly created groups, with the sometimes incomplete implementation of treatment particulars, with the borrowing of some treatment particulars by control group units, and with the limitations to external validity that often follow from how the random assignment is achieved.”
- Tom Cook & Monique Payne (2002, p. 174)

“After 4 decades of severe criticism, the ritual of null hypothesis significance testing - mechanical dichotomous decisions around a sacred 0.05 criterion - still persists. This article reviews the problems with this practice, including its near-universal misinterpretation of p as the probability that Ho . . . .[[the null hypothesis]]. . . . is false, the misinterpretation that its complement is the probability of successful replication, and the mistaken assumption that if one rejects Ho one thereby affirms the theory that led to the test. Exploratory data analysis and the use of graphic methods, a steady improvement in and a movement toward standardization in measurement, and emphasis on effect sizes using confidence intervals, and the informed use of available statistical methods is suggested. FOR GENERALIZATION, PSYCHOLOGISTS MUST FINALLY RELY, AS HAS BEEN DONE IN THE OLDER SCIENCES, ON REPLICATION.” [My CAPS.]
- Jacob Cohen (1994) in “The earth is round (p less than 0.05)”

REFERENCES [URL’s shortened by and accessed on 11 July 2011.]

Cook, T.D. & M.R. Payne. 2002. “Objecting to the Objections to Using Random Assignment in Educational Research” in Mosteller & Boruch (2002).

Cohen, J. 1994. “The earth is round (p less than 0.05),” American Psychologist 49: 997-1003; online as a 1.2 MB pdf at thanks to Christopher Green

Hake, R.R. 2011. “Re: controlled experiments,” online on the OPEN! AERA-L archives at Post of 11 Jul 2011 11:15:54-0700 to AERA-L, Net-Gold, and PhysLrnR. The abstract and link to the complete post are being transmitted to various discussion lists.

Mosteller, F. & R. Boruch, eds. 2002. Evidence Matters: Randomized Trials in Education Research. Brookings Institution. information at . A searchable expurgated Google Book Preview is online at .

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