Re: Correlations for Repeated measured variables

Posted by Rich Ulrich on Nov 03, 2018; 7:53am
URL: http://spssx-discussion.165.s1.nabble.com/Correlations-for-Repeated-measured-variables-tp5736935p5736943.html

Bruce's reply suggests this - in terms of Pearson r, you can have sets of those r's

for each one of your 210 cases, looking at those correlations across 4 time periods.

What I should want to produce would be some sort of average for those correlations.

The way that I know to do that uses discriminant function (if DF will allow 210 "groups").

Write the data out to "long" format, with four records (times) for each case, including

two "time" variables - one of them goes 1-4, and the other uses your actual interval Times.

Then you do the DF with Subjects as groups, using the Density, Distance, Time1 and Time2;

and ask for the "within groups correlation matrix" - that has the version of r that you want.

It uses pooled variances, and subtracts out effects of mean-differences between subjects.

I'm suggesting two Time variables because, when data are collected at four times, studies

USUALLY pick time intervals in which they expect equal amounts of change, so the 1-4

better represents an Expected linear trend than using the actual Times. If you don't have

a linear trend, then you might consider showing your results with something other than r.

--

Rich Ulrich

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From: SPSSX(r) Discussion <[hidden email]> on behalf of betty <[hidden email]>
Sent: Tuesday, October 30, 2018 11:13 AM
To: [hidden email]
Subject: Correlations for Repeated measured variables

 

For each of my 210 subjects, I have:

Parameter: Cell density (y1) at time T1;

parameter: Cell Density (y2) at time T2;

parameter: Cell Density (y3) at time T3;

parameter: Cell Density (y4) at time T4;

Parameter: Tube distance (g1) at time T1;

Parameter: Tube distance (g2) at time T2;

Parameter: Tube distance (g3) at time T3;

Parameter: Tube distance (g4) at time T4;

Time between T1 en T2 isn't the same as time between T2 and T3 etc.

I want to know:

Is there a correlation betweet Cell density and time

Is there a correlation between Tube distance and time

Is there a correlation between Cell density and Tube Distance

I have no clue how to do this in SPSS



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