Date: Thu, 29 Oct 2009 09:06:08 -0700 Arthur Burke "SPSSX(r) Discussion" Arthur Burke Re: how to compute this? To: Wang Xu A<200910280230.n9RJW5vB008058@malibu.cc.uga.edu> text/plain; charset="US-ASCII"

For details of how SPSS does the t-test, try ...

/Help/Statistics Coach/Compare Groups for Significant Differences/ ... /T Test Algorithms

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-----Original Message----- From: Wang Xu [mailto:dachengruoque@163.COM] Sent: Tuesday, October 27, 2009 7:30 PM To: SPSSX-L@LISTSERV.UGA.EDU Subject: how to compute this?

Hi all list members, I am a green hand at data analysis. Recently I was bumped by a scenario presented in a paper by Roger Kirk Kirk, R. E. (1996). Practical Significance: A Concept Whose Time Has Come. Educational and Psychological Measurement, 56(5), 746-759. on the page 755 of the paper the 2nd paragraph there is it. The summary of the scenario is as follows, 13 patients were assigned evenly to control and experimental groups.t(10) =1.61, p=.14, the mean for experimetal group is 13 IQ points higher than that of control group. At the end of the paragraph the author said that a 95% confidence interval for the population mean difference is likely to be between -6.3 and 32.3 IQ points. Do all the present conditions necessiate the computation of confidence interval for the population mean difference? I thought that there should be one more condition: standard deviation. Am I right? In spss there is always some computation of confidence interval for the population mean difference? How is it computed ? What is the formla for computing this? Thanks a lot!

W.X.

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