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Date:   Wed, 13 Jan 2010 20:53:40 -0300
Reply-To:   Hector Maletta <hmaletta@fibertel.com.ar>
Sender:   "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:   Hector Maletta <hmaletta@fibertel.com.ar>
Subject:   Re: Factor Analysis on dichotomous variables
Comments:   To: "Angelina S. MacKewn" <amackewn@utm.edu>
In-Reply-To:   <6F692813E2221C42B90DA62B4021FBD007DF7FAC@EXVS1.utm.edu>
Content-Type:   text/plain; charset="us-ascii"

Angie, My third message: Besides conceptual issues addressed in my previous messages, I should call your attention to the fact that 50 variables with 500 cases is very likely to yield non-significant results, due to small size of sample in relation to the number of variables. Some books or teachers speak about an absolute minimum of 10 cases per variable. With 500/50 you are precisely at that supposed minimum, but it is widely seen as too optimistic. 40-60 cases per variable is more like it, although there is no general rule because all depends on the amount of correlation among the observed variables. Have you considered dividing the 50 items into a number of groups evidently related to different dimensions? PCA performed on each group of more closely related dichotomous variables may be more reliable, both because they are more closely related and because the cases/variables ratio is higher.

Hector

-----Original Message----- From: SPSSX(r) Discussion [mailto:SPSSX-L@LISTSERV.UGA.EDU] On Behalf Of Angelina S. MacKewn Sent: 13 January 2010 19:41 To: SPSSX-L@LISTSERV.UGA.EDU Subject: Factor Analysis on dichotomous variables

What is the factor analysis (PCA) equivalent that can be run on dichotomous variables. I have 50 exhibited behaviours (yes/no) that I want to factor together. I have a sample size of about 500. I would be using SPSS and could use syntax if it is available.

Thanks, Angie

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