Date: Fri, 28 May 2010 04:35:17 -0700
Reply-To: Bruce Weaver <bruce.weaver@hotmail.com>
Sender: "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From: Bruce Weaver <bruce.weaver@hotmail.com>
Subject: Re: Appropriate test for measurements repeated at two levels
In-Reply-To: <201005280826.o4S5scmi001255@malibu.cc.uga.edu>
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Your measurements are nested within time periods, and time periods are nested
within subjects. So you could run a multilevel model (via MIXED). With
this approach, there is no need to have equal numbers of measurements per
time period (or time periods per subject), as there would be for repeated
measures ANOVA. The book by Singer & Willett is very helpful, and most of
their examples are demonstrated on the UCLA Computing website:
http://www.ats.ucla.edu/stat/examples/alda.htm
HTH.
Richard Devey wrote:
>
> I have a dataset containing heart rate measurements for two groups of
> subjects over four time periods. I need to assess if there are differences
> in heart rate between groups and over time. If I had one measurement per
> time period I could use repeated measures or the friedman test. The
> complication is that within each time period the subjects' heart rate is
> measured at intervals as resistance is increased. The number of
> measurements within the given time period can differ depending on the
> fitness of the subject e.g. subject 1 might have five heart rate
> measurements with increasing resistance while subject 2, fitter than
> subject 1, might have ten measurements. I could take a mean of these
> measurements to get one value per time period and proceed with repeated
> measures analysis. However, I'd be interested to know if there is a test
> which can take into account (1) the two groups (2) the four time periods
> and (3) the multiple measures of heart rate within each of the four time
> periods. Any suggestions would be greatly appreciated.
>
> Richard Devey
> University of Johannesburg
> South Africa
>
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-----
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Bruce Weaver
bweaver@lakeheadu.ca
http://sites.google.com/a/lakeheadu.ca/bweaver/
"When all else fails, RTFM."
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