```Date: Tue, 20 Jul 2010 14:16:39 -0400 Reply-To: "Burleson,Joseph A." Sender: "SPSSX(r) Discussion" From: "Burleson,Joseph A." Subject: Re: three way interaction vs separate analysis with 2 way interactione Comments: To: Gene Maguin In-Reply-To: <172F60DA2BE647F987BBCCD3B2E929F8@ssw.buffalo.edu> Content-Type: text/plain; charset="us-ascii" One can get a significant interaction in which for each gender there are opposite-sign 2-way interactions, but neither is significantly different from zero. The 3-way interaction is still significant. The "simple 2-way" effects are then tested, each for their own significance; they may or may not be, each in their own right, significantly different from zero. But the original 3-way interaction was explicitly NOT testing whether either (or both) was significantly different from zero. IT was testing whether the 2-way interaction was parallel for the two genders. So: report the 3-way from the total n analysis. Then "decompose" the interaction, if desired and report the significance of each from zero. Joe Burleson -----Original Message----- From: SPSSX(r) Discussion [mailto:SPSSX-L@LISTSERV.UGA.EDU] On Behalf Of Gene Maguin Sent: Tuesday, July 20, 2010 1:36 PM To: SPSSX-L@LISTSERV.UGA.EDU Subject: Re: three way interaction vs separate analysis with 2 way interactione Ann, >>the dichot. moderator is gender, so i just split the sample and calculated the 2 way interactions for men and women seperately. >>my assumption was that if i for example get a sign. interaction for men but not for women, that i can claim that there is a gender difference. Gene: You can claim it but as a reviewer I don't think I'd accept it. For instance, suppose the two-way interaction coefficient was -.03 (se=.06) for men and +.03 (se=.07) for women. Neither is significant and the signs are different. I wouldn't believe that women and differ. >>but as i understand you two, you both would recommend a three way interaction model. >>gene you wrote the following 'These two equation sets are apples and oranges. The answer to what to do has nothing to do with statistics. The correct answer is determined by the question you want an answer to. ' >>can you give an example when you would go for split sample with 2 way interactions. thanks for your helpful input! Gene: Not offhand. But, I'd bet that if you stated your hypothesis or question, it would imply a three way interaction. Gene Maguin ===================== To manage your subscription to SPSSX-L, send a message to LISTSERV@LISTSERV.UGA.EDU (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD ===================== To manage your subscription to SPSSX-L, send a message to LISTSERV@LISTSERV.UGA.EDU (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD ```

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