Date: Tue, 21 Jun 2011 15:38:38 -0700
Reply-To: "Parise, Carol A." <PariseC@sutterhealth.org>
Sender: "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From: "Parise, Carol A." <PariseC@sutterhealth.org>
Subject: Re: mixed models - time as DV
very good suggestion...
From: Rich Ulrich [mailto:firstname.lastname@example.org]
Sent: Tuesday, June 21, 2011 3:30 PM
To: Parise, Carol A.; email@example.com
Subject: RE: mixed models - time as DV
I don't remember ever seeing a psycho-physical graph that
tried to use Hour:Min for an axis, and I think I would not
like it if I did.
Convert time to Minutes, Min+ 60*Hours.
No one will expect anything different.
- I would say that the incidental, lifetime "practice" at any
given task is something that increases with age. That is a simple
reason why youth should show a greater practice effect between
two trials in the experiment.
> Date: Tue, 21 Jun 2011 15:10:11 -0700
> From: PariseC@sutterhealth.org
> Subject: Re: mixed models - time as DV
> To: SPSSX-L@LISTSERV.UGA.EDU
> Thank you for your question. I've posted a few times regarding my data that look like this:
> >ID Year Task Time Age
> >1 1986 ONE 2:15 40
> >1 1990 ONE 3:00 44
> >1 2000 ONE 1:59 45
> >1 2005 TWO 4:05 50
> >1 2007 TWO 3:58 52
> >1 2008 TWO 3:42 53
> >2 2001 TWO 3:00 30
> >2 2002 THREE 1:35 31
> >2 2003 THREE 1:55 33
> >2 2005 TWO 2:25 35
> >2 2006 THREE 2:40 36
> My goal is to determine if age, year and task have an effect on task time. Another variable i have in the data is number of times task is performed. i was originally thinking i needed to do repeated measures anova. but what these data don't show is that there are 28 tasks and 36 years and different people performed the tasks in different years. there are also several levels of correlation in the data: 1) the same person performed the same task in different years; 2) The same year had several different performers. This is why i turned to mixed models.
> The hypothesis is that age and number of times someone completes any task has an effect on task time. my descriptive analysis suggests that everyone improves their time on any task after doing any task twice. but the amount of improvement depends on age. people on the lowest quintiles of age improve alot more than people in higher quintiles of age. i also know that there is a task effect. Some of the tasks have mean finish times that are longer than others just because the tasks are harder.
> Another issue i came across is that my file has 14,000 cases. Some of my sample code has crashed SPSS. I'm not sure if this is operator erro - I am sticking terms in the model that are I shouldn't be or if this is me or some other issue.
> So, if you have another suggestion of how to deal with the data, i would love to hear it!