```Date: Fri, 12 Aug 2005 13:07:11 -0500 Reply-To: "Swank, Paul R" Sender: "SPSSX(r) Discussion" From: "Swank, Paul R" Subject: Re: effect size form F and df Comments: To: Matthew Pirritano Content-Type: text/plain; charset="us-ascii" d = the difference in means divided by the standard deviation. Assuming a two group design, F is the difference between means squared over the pooled variance multiplied by [1/n(1) + 1/n(2)] so that effect size squared is F times [1/n(1) + 1/n(2)]. If the n's are equal then this becomes F*(2/n) so that the effect size is the square root of [F*(2/n)]. Paul R. Swank, Ph.D. Professor, Developmental Pediatrics Medical School UT Health Science Center at Houston -----Original Message----- From: SPSSX(r) Discussion [mailto:SPSSX-L@LISTSERV.UGA.EDU] On Behalf Of Matthew Pirritano Sent: Friday, August 12, 2005 9:51 AM To: SPSSX-L@LISTSERV.UGA.EDU Subject: effect size form F and df Hello all, I want to calculate cohen's d from and F and df. Does anyone know how to do this, or if it is possible? I was thinking that I could just use this equation, since F is just t squared. I could take the square root of the F and then run this syntax. Does that make sense? ** *SPSS*: COMPUTE est_dbyt = (2 * t_value) / sqrt(df) . EXECUTE . Thanks Matt Matthew Pirritano, Ph.D. National Science Foundation Post-Doctoral Fellow College of Education Department of Individual, Family & Community Education MSC05 3040 1 University of New Mexico Albuquerque, NM 87131-0001 Telephone (505)277-7115 FAX (505)277-8361 ```

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