# Tetrachoric correlation then PAF?

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## Tetrachoric correlation then PAF?

 1. Given the number of variables, how to create a tetrachoric correlation matrix in SPSS version 16?   2.  How to do a Principal Axis Factoring with Varimax rotation method in SPSS 16 using a correlation matrix as input data?   Thanks.   Eins ---------------------------------   Get your preferred Email name! Now you can @ymail.com and @rocketmail.com. ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (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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## Re: Tetrachoric correlation then PAF?

 Eins, I can't comment on how to compute a tetrachoric matrix in spss. I don't know the formula and would have to look it up. Possibly the computation could be done using the matrix-end matrix command set (look this up in the syntax reference). I'd bet there are several people on the list that know exactly how to do it. I don't. As far as reading in a matrix goes, that's kind of easy. Look at the Matrix Data command, also in the syntax reference. Note that, as far as I know, the matrix has to be written so that it is as many columns wide as the number of variables. That might seem obvious but the point is that some programs ouput (or can output) a matrix in different arrangements on the page (and by this, I do not mean lower triangular vs rectangular). The very fact that you are asking about reading a matrix in means that you are computing that matrix in another program. I think the PAF part is kind of trivial. Again, look at the syntax ref. The key part is getting the matrix file in and selecting the extraction method (choose the PAF option). A varimax rotation is the default. Repost to the list if you have more questions. Gene Maguin ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (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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## Working proportions and GLM or equivalent

 In reply to this post by E. Bernardo All, I'm working with someone whose DV is a proportion. Specifically, a count of tasks completed a worker divided by total tasks undertaken in a unit time. There are about 10 workers per unit, three units per condition, and two conditions. Disregarding the DV type issue, I'm regarding this as a nested design, units within condition. I really never work with proportions and don't have hardly any experience. I'm thinking that one problem with proportions is that the standard deviation of a set of proportions depends on the mean proportion because the standard deviation of a proportion is simply sqrt(p*q). To fix up this problem, one solution has been to transform the raw proportions. So I'd like to hear advice on two lines of questions. 1) Is there a newer and more preferred way to analyze proportions within a GLM framework than transformations? 2) What are the recommended types of transformations to use with proportions? Any excellent refs are appreciated. Thanks, Gene Maguin ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (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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## Re: Tetrachoric correlation then PAF?

 In reply to this post by Maguin, Eugene Tetrachoric correlation is just polychoric correlation with dichotomous variables, I think.  There is an SPSS Statistics 17 extension command, SPSSINC HETCOR, that computes polychoric correlations.  You can download it from SPSS Developer Central (www.spss.com/devcentral).  Besides Version 17, it requires R 2.7.0.  Full requirements are in the readme file. HTH, Jon Peck -----Original Message----- From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of Gene Maguin Sent: Monday, October 13, 2008 9:04 AM To: [hidden email] Subject: Re: [SPSSX-L] Tetrachoric correlation then PAF? Eins, I can't comment on how to compute a tetrachoric matrix in spss. I don't know the formula and would have to look it up. Possibly the computation could be done using the matrix-end matrix command set (look this up in the syntax reference). I'd bet there are several people on the list that know exactly how to do it. I don't. As far as reading in a matrix goes, that's kind of easy. Look at the Matrix Data command, also in the syntax reference. Note that, as far as I know, the matrix has to be written so that it is as many columns wide as the number of variables. That might seem obvious but the point is that some programs ouput (or can output) a matrix in different arrangements on the page (and by this, I do not mean lower triangular vs rectangular). The very fact that you are asking about reading a matrix in means that you are computing that matrix in another program. I think the PAF part is kind of trivial. Again, look at the syntax ref. The key part is getting the matrix file in and selecting the extraction method (choose the PAF option). A varimax rotation is the default. Repost to the list if you have more questions. Gene Maguin ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (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 [hidden email] (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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## Re: Tetrachoric correlation then PAF?

 There is also a macro, r_tetra, available for computing polychoric (tetrachoric) correlations. http://www2.jura.uni-hamburg.de/instkrim/kriminologie/Mitarbeiter/Enzmann/Software/Enzmann_Software.html--Justin On Mon, Oct 13, 2008 at 1:58 PM, Peck, Jon <[hidden email]> wrote: > Tetrachoric correlation is just polychoric correlation with dichotomous > variables, I think.  There is an SPSS Statistics 17 extension command, > SPSSINC HETCOR, that computes polychoric correlations.  You can download it > from SPSS Developer Central (www.spss.com/devcentral).  Besides Version > 17, it requires R 2.7.0.  Full requirements are in the readme file. > > HTH, > Jon Peck > > -----Original Message----- > From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of > Gene Maguin > Sent: Monday, October 13, 2008 9:04 AM > To: [hidden email] > Subject: Re: [SPSSX-L] Tetrachoric correlation then PAF? > > Eins, > > I can't comment on how to compute a tetrachoric matrix in spss. I don't > know > the formula and would have to look it up. Possibly the computation could be > done using the matrix-end matrix command set (look this up in the syntax > reference). I'd bet there are several people on the list that know exactly > how to do it. I don't. > > As far as reading in a matrix goes, that's kind of easy. Look at the Matrix > Data command, also in the syntax reference. Note that, as far as I know, > the > matrix has to be written so that it is as many columns wide as the number > of > variables. That might seem obvious but the point is that some programs > ouput > (or can output) a matrix in different arrangements on the page (and by > this, > I do not mean lower triangular vs rectangular). The very fact that you are > asking about reading a matrix in means that you are computing that matrix > in > another program. > > I think the PAF part is kind of trivial. Again, look at the syntax ref. The > key part is getting the matrix file in and selecting the extraction method > (choose the PAF option). A varimax rotation is the default. > > Repost to the list if you have more questions. > > Gene Maguin > > ===================== > To manage your subscription to SPSSX-L, send a message to > [hidden email] (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 > [hidden email] (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 [hidden email] (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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## Re: Working proportions and GLM or equivalent

 In reply to this post by Maguin, Eugene Assuming that you have both the count of tasks completed and the total tasks undertaken available, have a look at using Generalized Linear Models (GENLIN) with a binomial distribution and the response specified as the number of events occurring in a set of trials. Alex -----Original Message----- From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of Gene Maguin Sent: Monday, October 13, 2008 11:58 AM To: [hidden email] Subject: Working proportions and GLM or equivalent All, I'm working with someone whose DV is a proportion. Specifically, a count of tasks completed a worker divided by total tasks undertaken in a unit time. There are about 10 workers per unit, three units per condition, and two conditions. Disregarding the DV type issue, I'm regarding this as a nested design, units within condition. I really never work with proportions and don't have hardly any experience. I'm thinking that one problem with proportions is that the standard deviation of a set of proportions depends on the mean proportion because the standard deviation of a proportion is simply sqrt(p*q). To fix up this problem, one solution has been to transform the raw proportions. So I'd like to hear advice on two lines of questions. 1) Is there a newer and more preferred way to analyze proportions within a GLM framework than transformations? 2) What are the recommended types of transformations to use with proportions? Any excellent refs are appreciated. Thanks, Gene Maguin ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (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 [hidden email] (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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## Re: Working proportions and GLM or equivalent

 Given the nested design, I think you are looking at a general non-linear mixed model. This can be done in HLM, MLWin, SAS, and a few others, but not as far as I know in SPSS. Paul R. Swank, Ph.D Professor and Director of Research Children's Learning Institute University of Texas Health Science Center Houston, TX 77038 -----Original Message----- From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of Reutter, Alex Sent: Monday, October 13, 2008 3:23 PM To: [hidden email] Subject: Re: Working proportions and GLM or equivalent Assuming that you have both the count of tasks completed and the total tasks undertaken available, have a look at using Generalized Linear Models (GENLIN) with a binomial distribution and the response specified as the number of events occurring in a set of trials. Alex -----Original Message----- From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of Gene Maguin Sent: Monday, October 13, 2008 11:58 AM To: [hidden email] Subject: Working proportions and GLM or equivalent All, I'm working with someone whose DV is a proportion. Specifically, a count of tasks completed a worker divided by total tasks undertaken in a unit time. There are about 10 workers per unit, three units per condition, and two conditions. Disregarding the DV type issue, I'm regarding this as a nested design, units within condition. I really never work with proportions and don't have hardly any experience. I'm thinking that one problem with proportions is that the standard deviation of a set of proportions depends on the mean proportion because the standard deviation of a proportion is simply sqrt(p*q). To fix up this problem, one solution has been to transform the raw proportions. So I'd like to hear advice on two lines of questions. 1) Is there a newer and more preferred way to analyze proportions within a GLM framework than transformations? 2) What are the recommended types of transformations to use with proportions? Any excellent refs are appreciated. Thanks, Gene Maguin ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (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 [hidden email] (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 [hidden email] (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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## Re: Working proportions and GLM or equivalent

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## Re: Working proportions and GLM or equivalent

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## Re: Tetrachoric correlation then PAF?

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## Re: Tetrachoric correlation then PAF?

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## Re: Working proportions and GLM or equivalent

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## Re: Working proportions and GLM or equivalent

 I'm running the following genlin procedure. GENLIN TasksDone of TotalTasks by unit condition/model unit(condition)    distribution=binomial link=logit. Condition has two levels and unit has six levels. N per level of unit ranges between 4 and 9. I got this warning. Warnings The maximum number of step-halvings was reached but the log-likelihood value cannot be further improved. Output for the last iteration is displayed. The GENLIN procedure continues despite the above warning(s). Subsequent results shown are based on the last iteration. Validity of the model fit is uncertain. I am completely willing to accept the criticism that my sample is too small. However, within that limitation, is there an estimation parameter that I can vary to try to get a valid solution? Thanks, Gene Maguin ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (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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## Re: Working proportions and GLM or equivalent

 What does your iteration history look like?  Use /PRINT HISTORY(1).  In particular, what are the last few values of the parameter estimates, and which ones appear to not be converging? Alex -----Original Message----- From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of Gene Maguin Sent: Tuesday, October 14, 2008 2:09 PM To: [hidden email] Subject: Re: Working proportions and GLM or equivalent I'm running the following genlin procedure. GENLIN TasksDone of TotalTasks by unit condition/model unit(condition)    distribution=binomial link=logit. Condition has two levels and unit has six levels. N per level of unit ranges between 4 and 9. I got this warning. Warnings The maximum number of step-halvings was reached but the log-likelihood value cannot be further improved. Output for the last iteration is displayed. The GENLIN procedure continues despite the above warning(s). Subsequent results shown are based on the last iteration. Validity of the model fit is uncertain. I am completely willing to accept the criticism that my sample is too small. However, within that limitation, is there an estimation parameter that I can vary to try to get a valid solution? Thanks, Gene Maguin ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (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