Posted by
parisec on
Jun 27, 2011; 10:55pm
URL: http://spssx-discussion.165.s1.nabble.com/Re-mixed-models-time-as-DV-SEC-UNOFFICIAL-tp4515228p4530146.html
Gene,
I'm not quite sure whether I have a two level or three level structure. In the examples I am reading, it seems obvious. For example, groups of students have the same teacher within a school. My thought is that i''ve got three tiers: task, year, person.
I have 28 tasks. I can think of this as task being the top tier since some tasks are known to be more difficult than others. Where things get muddled is that year is inherently tied to the task because weather plays a huge role within a task.
When you suggest an offset age as a polynomial are you thinking:
1) compute agediff = age at each task - age at first task
2) compute agediff squared
3) enter age at first task
4) enter agediff squared
Thanks. Everyone's comments have been very helpful.
Carol
-----Original Message-----
From: SPSSX(r) Discussion [mailto:
[hidden email]] On Behalf Of Gene Maguin
Sent: Wednesday, June 22, 2011 1:28 PM
To:
[hidden email]
Subject: Re: mixed models - time as DV [SEC: UNOFFICIAL]
Carol,
I was thinking that if you computed a new age variable that was the offset from the firat age at any task you could treat age at first task as a level two (person) variable and the age offset as a level 1 variable. Offset age could be modeled as a polynomial.
Year at first test would be a second person variable. Categorizing age makes results display easier, for sure. The empirical question is whether categorizing is more informative in a variance modeled sense.
Are you thinking of this dataset as having a two level or a three level structure?
Gene Maguin
-----Original Message-----
From: SPSSX(r) Discussion [mailto:
[hidden email]] On Behalf Of Parise, Carol A.
Sent: Wednesday, June 22, 2011 3:57 PM
To:
[hidden email]
Subject: Re: mixed models - time as DV [SEC: UNOFFICIAL]
My thought was that person, year, and task would be considered random variables and quintile of age and 'task time' i.e. 1st, 2nd, 3rd, etc would be fixed.
I know someone is going to say "you shouldn't group data if you don't have to". I have read these references.
My descriptive data show that there is an improvement between task 1 and task 2 (regardless of the task) and that improvement diminishes after around
3 tries. However, younger age leads to higher improvement than older age. So I need to include an interaction.
Stratfiying into quintiles makes this easy to see graphically but i'm not sure if this is the best way to handle this in the model. I've been reading a bit about entering splines into these models but i only know enough to be dangerous at this point.
________________________________________
From: Gosse, Michelle [
[hidden email]]
Sent: Wednesday, June 22, 2011 12:44 PM
To: Parise, Carol A.;
[hidden email]
Subject: RE: mixed models - time as DV [SEC: UNOFFICIAL]
Hi Carol,
How are you handling the "year" variable, I apologise if I have missed this information from previous postings?
Cheers
Michelle
-----Original Message-----
From: SPSSX(r) Discussion [mailto:
[hidden email]] On Behalf Of Parise, Carol A.
Sent: Thursday, 23 June 2011 7:41 AM
To:
[hidden email]
Subject: Re: mixed models - time as DV
great! hard to believe but these are actual times. it's kind of a crazy 'task'.
________________________________
From: Art Kendall [
[hidden email]]
Sent: Wednesday, June 22, 2011 12:39 PM
To: Parise, Carol A.; SPSSX-L post
Subject: Re: [SPSSX-L] mixed models - time as DV
This worked okay on my machine.
I guess then that these are durations (intervals) rather specific times?
data list list/thetime(time12.2).
begin data
31:22:33
24:00:00
23:59:55
42:10:10
end data.
compute secs = thetime.
formats secs (f16).
compute back = secs.
formats back (time12.2).
execute.
list.
Art
On 6/22/2011 3:29 PM, Parise, Carol A. wrote:
Thanks Art. I don't have the data in front of me today but i will check this out.
Do you know if are differences when time is over 24:00:00 versus under 24:00:00? when working with hh:mm:ss, in the past, i recall having some issues with this. some of these "tasks" took more than a day.
________________________________
From: Art Kendall [
[hidden email]<mailto:
[hidden email]>]
Sent: Wednesday, June 22, 2011 5:39 AM
To: Parise, Carol A.
Cc:
[hidden email]<mailto:
[hidden email]>
Subject: Re: [SPSSX-L] mixed models - time as DV
What format did you use to put the DV in?
try this syntax. It appears that time12.2 format works on my machine.
data list list/thetime(time12.2).
begin data
1:22:33
24:00:00
23:59:55
12:10:10
end data.
compute secs = thetime.
formats secs (f16).
compute back = secs.
formats back (time12.2).
execute.
list.
I then saved that file and opened a new data file.
I copied secs into the new data file.
I changed the type to date and used the drop down list to get a time format.
Also, the only time I would expect the intercept to be exactly equal to the grand mean would be when all predictors were zero like with z-scores.
Art Kendall
Social Research Consultants
On 6/21/2011 6:37 PM, Parise, Carol A. wrote:
Art,
This appears to work if I use the format: dd-mm-yyyy hh:mm:ss. Any other format and the numbers are not logical. But, the date that showis up is kind of crazy: 16-MAR-1590. I'm a bit concerned that this may not be accurate.
Although the time is in the ballpark, I would think that the overall mean i get using descriptives should be just about the same as what i get from this model and it's off by a good amount and it's not.
Thank you!
Carol
________________________________
From: Art Kendall [mailto:
[hidden email]]
Sent: Tuesday, June 21, 2011 2:58 PM
To: Parise, Carol A.
Cc:
[hidden email]<mailto:
[hidden email]><mailto:SPSSX-L@LIS
TSERV.UGA.EDU><mailto:
[hidden email]>
Subject: Re: [SPSSX-L] mixed models - time as DV
try this as a workaround.
Time is in seconds since the start of the Gregorian calendar.
While you have the .spv file open, open a new data file <file><new><data> Switch to the the output file. highlight and copy the intercept.
Switch to the data file. Paste the intercept.
Click the variables view tab.
change the format to time.
Art Kendall
Social Research Consultants
On 6/21/2011 5:40 PM, Parise, Carol A. wrote:
Hi all,
This one of probably many questions i will likely be posting on using linear mixed models over the next few months. It's my first crack at using this and i'm slowly working through the lingo by reading as much as I can. I read the SPSS technical report on this and i found an example from nice little article that i am using to mess with my data.
http://www.indiana.edu/~statmath/stat/all/hlm/hlm.pdf<
http://www.indiana.edu/%7Estatmath/stat/all/hlm/hlm.pdf><
http://www.indiana.edu/%7Estatmath/stat/all/hlm/hlm.pdf>
The article explains the interpretation of the intercept term in the empty model is equivalent to the overall math achievement score.
My data have time in hh:mm:ss as the DV.
In my sample analysis, the scale of the intercept is not in hh:mm:ss and i can't seem to adjust to to be in this format with the "cell properties" when i click on the output.
It would be really helpful to have the correct scale versus just the p-value for interpretation purposes. Anyone have thoughts on how I can do this?
I am running version 14.0 and we won't be upgrading anytime soon.
Thanks much.
Carol
=====================
To manage your subscription to SPSSX-L, send a message to
[hidden email]<mailto:
[hidden email]><mailto:LISTSERV@
LISTSERV.UGA.EDU><mailto:
[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
UNOFFICIAL
**********************************************************************
This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager.
This footnote also confirms that this email message has been swept by MIMEsweeper for the presence of computer viruses.
**********************************************************************
=====================
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