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Assignment 7

Multivariate Data Analysis
Psychology 6140




A study by Robert Hart examined the ability of standard laboratory memory tasks to distinguish between patients with mild Alzheimer's disease, from those with depression and control subjects. The memory tasks included free recall and selective reminding with both high and low imagery words, a measure of short term memory storage, and a recognition memory task. The data are stored in the file alzheim sas on the server (there's also an SPSS version in psy6140/lib/spss/), and you can use them by starting your SAS program with the line
%include data(alzheim);
The data file gives the following names to the variables:
  label subj    = 'Subject ID'
        trecall = 'Total recall'
        hirecall= 'HI Imagery Recall'
        lirecall= 'LO Imagery Recall'
        tunrem  = 'Unreminded Memory'
        hiunrem = 'HI Imagery Unreminded Memory'
        liunrem = 'LO Imagery Unreminded Memory'
        store   = 'Storage'
        recog   = 'Recognition Memory';
(Note that TRECALL and TUNREM are each calculated as the sum or average of the two RECALL and UNREM measures.)
  1. Using Proc GLM, test the hypothesis of equal mean vectors for the three groups at alpha = 0.05 by an appropriate multivariate test.
  2. If the multivariate test is significant, determine which variables are individually showing significant overall group differences by univariate tests.
  3. Obtain a printout of the H and E matrices for the overall one-way MANOVA. Show how the univariate F statistics relate to the elements of the H and E matrices. Interpret the elements in the matrix labelled "Partial correlation coefficients from the Error SS&CP Matrix".
  4. Carry out multivariate tests of the following contrasts: (a) of the Alzheimer's group vs. (Depressed and Normals), (b) of the Depressed vs. the Normal subjects.
  5. For the overall one-way MANOVA, use the CANONICAL option to determine whether the memory tests distinguish among the group mean vectors along one or more than one dimension.
  6. Write a short (half-page or less) abstract summarizing the results of these analyses. One's normal expectations are that Alzheimer's patients should differ from non-Alzheimer subjects on at least some of the tasks. Include in your abstract information that comes from the multivariate tests, as well as information about the effects on each variable and the contrasts tested.

Author: Michael Friendly © 1995 Email:friendly@yorku.ca

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