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I have a table below of comparing responses for the same question from a pre and post survey.
I want to know the 55.1% is statistically different from 42.5%.
I have no idea how to do this and have been stuck trying to figure this out. Any help you can give is appreciated.
Table of survey by q15_both | |||
survey | q15_both | ||
0 | 1 | Total | |
Post | 27 | 22 | 49 |
30.34 | 24.72 | 55.06 | |
55.1 | 44.9 | ||
61.36 | 48.89 | ||
Pre | 17 | 23 | 40 |
19.1 | 25.84 | 44.94 | |
42.5 | 57.5 | ||
38.64 | 51.11 | ||
Total | 44 | 45 | 89 |
49.44 | 50.56 | 100 | |
Frequency Missing = 2 |
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Is this the output of a FREQ statement? If so, add a /CHISQ to your table statement and it'll test it for you.
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I'm not an expert, but it sounds like you might want to look up McNemar's test, which is one of the tests for agreement.
See the documentation at http://support.sas.com/documentation/cdl/en/statug/63962/HTML/default/viewer.htm#statug_freq_a000000...
For an example, see http://www.ats.ucla.edu/stat/sas/whatstat/whatstat.htm (search for "McNemar's Test" on the page)
data a;
input survey q freq;
datalines;
0 0 27
0 1 22
1 0 17
1 1 23
;
proc freq data=a;
weight freq;
tables survey*q / agree;
/* or EXACT mcnem; for small samples */
run;
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Rick's right, McNemar's is the test for pre-post observations. The documentation talks about matched pairs, and pre-post is one kind of matching. It is testing whether the pairs that were 0-1 are different from the pairs that are 1-0, which is not quite the marginal test that you asked about initially. Be careful how you set it up; the sample size for McNemar's test is the number of pairs. In the table you show, it looks like you have broken the matching and have some missing data (N=49 for Post and 40 for Pre?).
If you cannot link the pre-observations to the post-observations, then you are back to the marginal test of homogenity that SusieQ pointed you to.
Doc Muhlbaier
Duke