Group Based Trajectory Analysis
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Does anybody know if it is possible to do group based trajectory analysis
in SPSS? I would like to find latent groups of trajectories for juvenile arrests. Thank you in advance! ===================== 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 |
Re: Group Based Trajectory Analysis
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As far as I know, the answer is no. You must use SAS. If anyone knows how to
do this type of analysis in SPSS, I would love to hear about it. Mariajosé Romero, PhD Associate Professor & Coordinator Education Programs LaGuardia Community College, CUNY -----Original Message----- From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of Kat Sent: Friday, September 30, 2011 11:42 AM To: [hidden email] Subject: Group Based Trajectory Analysis Does anybody know if it is possible to do group based trajectory analysis in SPSS? I would like to find latent groups of trajectories for juvenile arrests. Thank you in advance! ===================== 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 |
Re: Group Based Trajectory Analysis
Administrator
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Sometimes, the same statistical animal goes by different names in different disciplines. In case that's happening here, what procedure would you use in SAS for this type of analysis? And are you aware of any other names for "group based trajectory analysis"? ("Trajectory" is a word that crops up in analysis of longitudinal data with multilevel models, with occasions clustered within subjects. So I wonder if this is what you're getting at.)
--
Bruce Weaver bweaver@lakeheadu.ca http://sites.google.com/a/lakeheadu.ca/bweaver/ "When all else fails, RTFM." PLEASE NOTE THE FOLLOWING: 1. My Hotmail account is not monitored regularly. To send me an e-mail, please use the address shown above. 2. The SPSSX Discussion forum on Nabble is no longer linked to the SPSSX-L listserv administered by UGA (https://listserv.uga.edu/). |
Re: Group Based Trajectory Analysis
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Kat,
Tell us what you mean by 'Group' and as Bruce indicated what you mean by 'trajectory'. More specifically, do you have predefined groups, like males and females; 8th, 9th and 10th grade students? OR do you have a big bunch of people and you want to find groups of people who have 'similar' trajectories? On to trajectory. Do you have measures of something at multiple time points (how many??) for each person? Or something else? And. How are you thinking of trajectory? Is it something that the group has, meaning that the variance of the trajectory coefficients for the group is 0.0 or is it something that has a distribution among members of a group, meaning that the trajectory coefficents for the group have non-zero variance. Gene Maguin -----Original Message----- From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of Bruce Weaver Sent: Friday, September 30, 2011 3:23 PM To: [hidden email] Subject: Re: Group Based Trajectory Analysis Sometimes, the same statistical animal goes by different names in different disciplines. In case that's happening here, what procedure would you use in SAS for this type of analysis? And are you aware of any other names for "group based trajectory analysis"? ("Trajectory" is a word that crops up in analysis of longitudinal data with multilevel models, with occasions clustered within subjects. So I wonder if this is what you're getting at.) Mariajose Romero, PhD wrote: > > As far as I know, the answer is no. You must use SAS. If anyone knows how > to > do this type of analysis in SPSS, I would love to hear about it. > > Mariajosé Romero, PhD > Associate Professor & Coordinator Education Programs > LaGuardia Community College, CUNY > > -----Original Message----- > From: SPSSX(r) Discussion [mailto:SPSSX-L@.UGA] On Behalf Of Kat > Sent: Friday, September 30, 2011 11:42 AM > To: SPSSX-L@.UGA > Subject: Group Based Trajectory Analysis > > Does anybody know if it is possible to do group based trajectory analysis > in SPSS? I would like to find latent groups of trajectories for juvenile > arrests. > Thank you in advance! > > ===================== > To manage your subscription to SPSSX-L, send a message to > LISTSERV@.UGA (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@.UGA (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 > ----- -- Bruce Weaver [hidden email] http://sites.google.com/a/lakeheadu.ca/bweaver/ "When all else fails, RTFM." NOTE: My Hotmail account is not monitored regularly. To send me an e-mail, please use the address shown above. -- View this message in context: http://spssx-discussion.1045642.n5.nabble.com/Group-Based-Trajectory-Analysi s-tp4857707p4858134.html Sent from the SPSSX Discussion mailing list archive at Nabble.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 ===================== 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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In reply to this post by Kat-2
I do not have predifined groups. Your second guess is right, I have a big
bunch of people and want to find groups who have similar trajectories. I have measures of something on a continuous basis- specifically arrests. That data could be grouped if necessary into number of arrests per year for several years for each person. Relating to your question about variance, I'm not entirely sure because this is a new method I am trying to learn, but I believe that there would be variance within the groups. The goal is to determine if there are underlying trajectories or patterns of offending. On Fri, 30 Sep 2011 16:01:06 -0400, Gene Maguin <[hidden email]> wrote: >Kat, > >Tell us what you mean by 'Group' and as Bruce indicated what you mean by >'trajectory'. More specifically, do you have predefined groups, like males >and females; 8th, 9th and 10th grade students? OR do you have a big bunch of >people and you want to find groups of people who have 'similar' >trajectories? On to trajectory. Do you have measures of something at >multiple time points (how many??) for each person? Or something else? And. >How are you thinking of trajectory? Is it something that the group has, >meaning that the variance of the trajectory coefficients for the group is >0.0 or is it something that has a distribution among members of a group, >meaning that the trajectory coefficents for the group have non-zero >variance. > >Gene Maguin > > > >-----Original Message----- >From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of >Bruce Weaver >Sent: Friday, September 30, 2011 3:23 PM >To: [hidden email] >Subject: Re: Group Based Trajectory Analysis > >Sometimes, the same statistical animal goes by different names in different >disciplines. In case that's happening here, what procedure would you use >SAS for this type of analysis? And are you aware of any other names for >"group based trajectory analysis"? ("Trajectory" is a word that crops up in >analysis of longitudinal data with multilevel models, with occasions >clustered within subjects. So I wonder if this is what you're getting at.) > > > >Mariajose Romero, PhD wrote: >> >> As far as I know, the answer is no. You must use SAS. If anyone knows how >> to >> do this type of analysis in SPSS, I would love to hear about it. >> >> Mariajos� Romero, PhD >> Associate Professor & Coordinator Education Programs >> LaGuardia Community College, CUNY >> >> -----Original Message----- >> From: SPSSX(r) Discussion [mailto:SPSSX-L@.UGA] On Behalf Of Kat >> Sent: Friday, September 30, 2011 11:42 AM >> To: SPSSX-L@.UGA >> Subject: Group Based Trajectory Analysis >> >> Does anybody know if it is possible to do group based trajectory analysis >> in SPSS? I would like to find latent groups of trajectories for juvenile >> arrests. >> Thank you in advance! >> >> ===================== >> To manage your subscription to SPSSX-L, send a message to >> LISTSERV@.UGA (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@.UGA (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 >> > > >----- >-- >Bruce Weaver >[hidden email] >http://sites.google.com/a/lakeheadu.ca/bweaver/ > >"When all else fails, RTFM." > >NOTE: My Hotmail account is not monitored regularly. >To send me an e-mail, please use the address shown above. > >-- >View this message in context: >http://spssx-discussion.1045642.n5.nabble.com/Group-Based-Trajectory- >s-tp4857707p4858134.html >Sent from the SPSSX Discussion mailing list archive at Nabble.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 > >===================== >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 |
Re: Group Based Trajectory Analysis
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Ooooh. You say you have arrests measured on a continuous basis. So what does
that mean? Does that mean you know the arrest dates? And, does everybody have at least one arrest? I see you are in state government. To the extent that you can, would you describe your dataset in terms of who's in it, the range in the time spans for which you have data for dataset members and the range in the number of arrests per time unit, like maybe, a year. Gene Maguin -----Original Message----- From: Courtney, Katherine, CYFD [mailto:[hidden email]] Sent: Friday, September 30, 2011 4:50 PM To: [hidden email]; [hidden email] Subject: Re: Group Based Trajectory Analysis I do not have predifined groups. Your second guess is right, I have a big bunch of people and want to find groups who have similar trajectories. I have measures of something on a continuous basis- specifically arrests. That data could be grouped if necessary into number of arrests per year for several years for each person. Relating to your question about variance, I'm not entirely sure because this is a new method I am trying to learn, but I believe that there would be variance within the groups. The goal is to determine if there are underlying trajectories or patterns of offending. On Fri, 30 Sep 2011 16:01:06 -0400, Gene Maguin <[hidden email]> wrote: >Kat, > >Tell us what you mean by 'Group' and as Bruce indicated what you mean by >'trajectory'. More specifically, do you have predefined groups, like males >and females; 8th, 9th and 10th grade students? OR do you have a big bunch of >people and you want to find groups of people who have 'similar' >trajectories? On to trajectory. Do you have measures of something at >multiple time points (how many??) for each person? Or something else? And. >How are you thinking of trajectory? Is it something that the group has, >meaning that the variance of the trajectory coefficients for the group is >0.0 or is it something that has a distribution among members of a group, >meaning that the trajectory coefficents for the group have non-zero >variance. > >Gene Maguin > > > >-----Original Message----- >From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of >Bruce Weaver >Sent: Friday, September 30, 2011 3:23 PM >To: [hidden email] >Subject: Re: Group Based Trajectory Analysis > >Sometimes, the same statistical animal goes by different names in different >disciplines. In case that's happening here, what procedure would you use >SAS for this type of analysis? And are you aware of any other names for >"group based trajectory analysis"? ("Trajectory" is a word that crops up in >analysis of longitudinal data with multilevel models, with occasions >clustered within subjects. So I wonder if this is what you're getting at.) > > > >Mariajose Romero, PhD wrote: >> >> As far as I know, the answer is no. You must use SAS. If anyone knows how >> to >> do this type of analysis in SPSS, I would love to hear about it. >> >> Mariajos� Romero, PhD >> Associate Professor & Coordinator Education Programs >> LaGuardia Community College, CUNY >> >> -----Original Message----- >> From: SPSSX(r) Discussion [mailto:SPSSX-L@.UGA] On Behalf Of Kat >> Sent: Friday, September 30, 2011 11:42 AM >> To: SPSSX-L@.UGA >> Subject: Group Based Trajectory Analysis >> >> Does anybody know if it is possible to do group based trajectory analysis >> in SPSS? I would like to find latent groups of trajectories for juvenile >> arrests. >> Thank you in advance! >> >> ===================== >> To manage your subscription to SPSSX-L, send a message to >> LISTSERV@.UGA (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@.UGA (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 >> > > >----- >-- >Bruce Weaver >[hidden email] >http://sites.google.com/a/lakeheadu.ca/bweaver/ > >"When all else fails, RTFM." > >NOTE: My Hotmail account is not monitored regularly. >To send me an e-mail, please use the address shown above. > >-- >View this message in context: >http://spssx-discussion.1045642.n5.nabble.com/Group-Based-Trajectory- >s-tp4857707p4858134.html >Sent from the SPSSX Discussion mailing list archive at Nabble.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 > >===================== >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 |
Re: Group Based Trajectory Analysis
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In reply to this post by Kat-2
The group-based method, also known as "finite mixture modeling," can be done in Latent Gold, in SAS (using PROC TRAJ, which was created by Daniel Nagin and his associates) and in Stata (using Partha Deb's fmm routine). Starting out using this method to analyze trajectories is, in my opinion, a questionable way to proceed. The algorithms used by these routines will produce optimal solutions that have more distinct groups than are actually present in the data, if the distributions are skewed, as is commonly the case when analyzing involvement in crime. In research I have been doing with Michael Ezell, analyzing arrest histories of a large number of youths released from the California Youth Authority, we see little evidence of sharply distinct groups when we analyze the histories using multi-level modeling or individual time series, even though the group-based approach provides optimal fits with 6 groups. In a paper we are now completing, we recommend that researchers first check as to whether there are clearly distinct groups with little or no overlap, using methods that do not impose the group structure on the data, before turning to finite mixture modeling. David Greenberg, Sociology Department, New York University
On Fri, Sep 30, 2011 at 4:50 PM, Courtney, Katherine, CYFD <[hidden email]> wrote: I do not have predifined groups. Your second guess is right, I have a big |
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Hi
all,
I have
a question on interpretation of the random versus fixed effects coefficients
that come out of a mixed model.
Fixed
effects are somewhat straightfoward. From what i think i understand, the
coefficient represents a change in the DV for a 1 unit change in the variable -
just like in a generalized linear model. Statistical signficance for an IV is
determine by a t-test testing whether the coefficient is different from 0. if
the CIs of the coefficient don't cross zero, you're in
business.
For
random effects, the output is labeled 'estimate' but the table is
"covariance parameter estimates" and tells you the percent of variance accounted
for by the variable of interest. Statistical significance is tested using the
Wald Z.
My
confusion lies when i read the results of publications that use linear mixed
models. The examples i've been going through tend to discuss these factors
separately, discussing percent of variance accounted for by the random effects
and change in DV for increases in the IV for the fixed factors.
However, in several publications, both the random and
fixed effects are included in a single table and state something like
"Table 1 presents the mixed effects model results estimating the
simultaneous effects of **random and fixed effects**". They then go on and
interpret them all the same just as if they were all fixed effects.
I
suspect these publications are correct (at least i would hope peer review
would have caught this type of error) and I am the one who is missing
something.
Thanks
in advance for enlightenment.
Carol
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Re: Group Based Trajectory Analysis
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In reply to this post by David Greenberg
It can also be done in Mplus. Paul Dr. Paul R. Swank, Children's Learning Institute Professor, Department of Pediatrics, Medical School Adjunct Professor, School of Public Health University of Texas Health Science Center-Houston From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of David Greenberg The group-based method, also known as "finite mixture modeling," can be done in Latent Gold, in SAS (using PROC TRAJ, which was created by Daniel Nagin and his associates) and in Stata (using Partha Deb's fmm routine). Starting out using this method to analyze trajectories is, in my opinion, a questionable way to proceed. The algorithms used by these routines will produce optimal solutions that have more distinct groups than are actually present in the data, if the distributions are skewed, as is commonly the case when analyzing involvement in crime. In research I have been doing with Michael Ezell, analyzing arrest histories of a large number of youths released from the California Youth Authority, we see little evidence of sharply distinct groups when we analyze the histories using multi-level modeling or individual time series, even though the group-based approach provides optimal fits with 6 groups. In a paper we are now completing, we recommend that researchers first check as to whether there are clearly distinct groups with little or no overlap, using methods that do not impose the group structure on the data, before turning to finite mixture modeling. David Greenberg, Sociology Department, New York University On Fri, Sep 30, 2011 at 4:50 PM, Courtney, Katherine, CYFD <[hidden email]> wrote: I do not have predifined groups. Your second guess is right, I have a big >people and you want to find groups of people who have 'similar' >trajectories? On to trajectory. Do you have measures of something at >multiple time points (how many??) for each person? Or something else? And. >How are you thinking of trajectory? Is it something that the group has, >meaning that the variance of the trajectory coefficients for the group is >0.0 or is it something that has a distribution among members of a group, >meaning that the trajectory coefficents for the group have non-zero >variance. > >Gene Maguin > > > >-----Original Message----- >From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of >Bruce Weaver >Sent: Friday, September 30, 2011 3:23 PM >To: [hidden email] >Subject: Re: Group Based Trajectory Analysis > >Sometimes, the same statistical animal goes by different names in different >disciplines. In case that's happening here, what procedure would you use >SAS for this type of analysis? And are you aware of any other names for >"group based trajectory analysis"? ("Trajectory" is a word that crops up in >analysis of longitudinal data with multilevel models, with occasions >clustered within subjects. So I wonder if this is what you're getting at.) > > > >Mariajose Romero, PhD wrote: >> >> As far as I know, the answer is no. You must use SAS. If anyone knows how >> to >> do this type of analysis in SPSS, I would love to hear about it. >> >> Mariajos� Romero, PhD >> Associate Professor & Coordinator Education Programs >> LaGuardia Community College, CUNY >> >> -----Original Message----- >> From: SPSSX(r) Discussion [mailto:[hidden email].UGA] On Behalf Of Kat >> Sent: Friday, September 30, 2011 11:42 AM >> To: SPSSX-L@.UGA >> Subject: Group Based Trajectory Analysis >> >> Does anybody know if it is possible to do group based trajectory analysis >> in SPSS? I would like to find latent groups of trajectories for juvenile >> arrests. >> Thank you in advance! >> >> ===================== >> To manage your subscription to SPSSX-L, send a message to >> LISTSERV@.UGA (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@.UGA (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 >> > > >----- >-- >Bruce Weaver >[hidden email] >http://sites.google.com/a/lakeheadu.ca/bweaver/ > >"When all else fails, RTFM." > >NOTE: My Hotmail account is not monitored regularly. >To send me an e-mail, please use the address shown above. > >-- >View this message in context: >http://spssx-discussion.1045642.n5.nabble.com/Group-Based-Trajectory- >s-tp4857707p4858134.html >Sent from the SPSSX Discussion mailing list archive at Nabble.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 > >===================== >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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In reply to this post by parisec
Carol,
I suggest you take some time reading though the online documentation to which I have linked below. Write back if you have specific questions pertaining to fixed versus random effects. http://faculty.chass.ncsu.edu/garson/PA765/multilevel.htm Ryan On Fri, Sep 30, 2011 at 7:29 PM, Parise, Carol A. <[hidden email]> wrote: > Hi all, > > I have a question on interpretation of the random versus fixed effects > coefficients that come out of a mixed model. > > Fixed effects are somewhat straightfoward. From what i think i understand, > the coefficient represents a change in the DV for a 1 unit change in the > variable - just like in a generalized linear model. Statistical signficance > for an IV is determine by a t-test testing whether the coefficient is > different from 0. if the CIs of the coefficient don't cross zero, you're in > business. > > For random effects, the output is labeled 'estimate' but the table is > "covariance parameter estimates" and tells you the percent of variance > accounted for by the variable of interest. Statistical significance is > tested using the Wald Z. > > My confusion lies when i read the results of publications that use linear > mixed models. The examples i've been going through tend to discuss these > factors separately, discussing percent of variance accounted for by the > random effects and change in DV for increases in the IV for the fixed > factors. > > However, in several publications, both the random and fixed effects are > included in a single table and state something like "Table 1 presents the > mixed effects model results estimating the simultaneous effects of **random > and fixed effects**". They then go on and interpret them all the same just > as if they were all fixed effects. > > I suspect these publications are correct (at least i would hope peer review > would have caught this type of error) and I am the one who is missing > something. > > Thanks in advance for enlightenment. > > Carol > > > > > ===================== 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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Is the maps module only for visual display purposes, or does it also have
geo-statistical capacity. Is it limited to ESRI shape files or are other file formats possible. Brian Cooper ===================== 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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In reply to this post by Ryan
Ryan,
Thank you for the reference. I will review and see if this clears things up. Bruce, I had no idea that pushing reply and changing the subject to post a new message retained the old subject line! Thanks for the heads up. Carol -----Original Message----- From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of R B Sent: Sunday, October 02, 2011 8:07 PM To: [hidden email] Subject: Re: random vs fixed effects coefficients - LMM Carol, I suggest you take some time reading though the online documentation to which I have linked below. Write back if you have specific questions pertaining to fixed versus random effects. http://faculty.chass.ncsu.edu/garson/PA765/multilevel.htm Ryan On Fri, Sep 30, 2011 at 7:29 PM, Parise, Carol A. <[hidden email]> wrote: > Hi all, > > I have a question on interpretation of the random versus fixed effects > coefficients that come out of a mixed model. > > Fixed effects are somewhat straightfoward. From what i think i > understand, the coefficient represents a change in the DV for a 1 unit > change in the variable - just like in a generalized linear model. > Statistical signficance for an IV is determine by a t-test testing > whether the coefficient is different from 0. if the CIs of the > coefficient don't cross zero, you're in business. > > For random effects, the output is labeled 'estimate' but the table is > "covariance parameter estimates" and tells you the percent of variance > accounted for by the variable of interest. Statistical significance is > tested using the Wald Z. > > My confusion lies when i read the results of publications that use > linear mixed models. The examples i've been going through tend to > discuss these factors separately, discussing percent of variance > accounted for by the random effects and change in DV for increases in > the IV for the fixed factors. > > However, in several publications, both the random and fixed effects > are included in a single table and state something like "Table 1 > presents the mixed effects model results estimating the simultaneous > effects of **random and fixed effects**". They then go on and > interpret them all the same just as if they were all fixed effects. > > I suspect these publications are correct (at least i would hope peer > review would have caught this type of error) and I am the one who is > missing something. > > Thanks in advance for enlightenment. > > Carol > > > > > ===================== 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 |
Re: random vs fixed effects coefficients - LMM
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Administrator
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Carol, I think the UGA archive stores it with the new subject, but the Nabble archive stores it under the original thread.
Cheers, Bruce
--
Bruce Weaver bweaver@lakeheadu.ca http://sites.google.com/a/lakeheadu.ca/bweaver/ "When all else fails, RTFM." PLEASE NOTE THE FOLLOWING: 1. My Hotmail account is not monitored regularly. To send me an e-mail, please use the address shown above. 2. The SPSSX Discussion forum on Nabble is no longer linked to the SPSSX-L listserv administered by UGA (https://listserv.uga.edu/). |
Re: Group Based Trajectory Analysis
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In reply to this post by Kat-2
Dear Kat,
I'm learning to Tracking. One of the procedures - called ZDIST - is to establish the best polynomial function, then calculate the Euclidean distance between trajectories. This makes it possible to establish - through cluster analysis - subgroups with distinct trajectories. I use a software called "longitudinal data analisy - LDA. It is a free program for Schneiderman and Kowalski. Thanks for attention, |
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