I'm supervising a student who is collecting sequential data over
days. There is a baseline period, followed by the application of a
particular experimental condition. She would like to compare the data
collected during baseline with the data collected during treatment
(for example, seven days of baseline followed by seven days of
treatment). Initially she would like to examine the data one subject
at a time.
She could do this, I suppose, with an independent t-test for baseline
data compared with treatment data. But the data are in the form of a
time series, and I recall that something called trend analysis may be
appropriate.
I've just started learning SPSS (a fugitive from SYSTAT), and I can't
find anything in various how-to sources which deals with this issue.
The only relevant book in the library is one called "Non-parametric
trend analysis" and it's dated 1965, well before the age of SPSS. I'll
check it out anyway, but I wondered if anyone here had any thoughts on
this problem.
Specifically, does anyone know how I can do a test for a difference
between two trends on SPSS? This sounds like a problem that people
using reversal designs in behaviour modification (when they're not
swearing off statistics entirely) might have looked into.
Failing that, perhaps someone has an e-mail address for an SPSS
listserv that may deal with questions of this kind. SYSTAT had one,
and Leland Wilkinson Himself would sometimes answer questions on it.
-Stephen
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Stephen Black, Ph.D. tel: (819) 822-9600 ext 2470
Department of Psychology fax: (819) 822-9661
Bishop's University e-mail: [EMAIL PROTECTED]
Lennoxville, QC
J1M 1Z7
Canada Department web page at http://www.ubishops.ca/ccc/div/soc/psy
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