Date:         Mon, 3 Aug 2009 18:33:46 -0400
Reply-To:     Peter Flom <peterflomconsulting@mindspring.com>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Peter Flom <peterflomconsulting@MINDSPRING.COM>
Subject:      Re: Question on Comparing Two Averages
Comments: To: jasonm@UCLA.EDU
Content-Type: text/plain; charset=UTF-8

J M <jasonm@UCLA.EDU> wrote
>>
>> HOWEVER, with n = 4,500, a tiny difference will be statistically
>> significant. Will it be of any importance?
>
>So, if I have 20% respond "yes" in 2008 and then 22% respond "yes" in
>2009 I can say that due to the large sample the difference would most
>likely be statistically significant if we had the correct data to
>actually test this claim?
>

You can do an independent sample t-test of proportions, ignoring the matching.  This is easy enough
to do by hand, with the formula for a t-test.

Or you can do a chi-square test:

data today;
 input year $ yesno $ count;
 datalines;
 2009  yes 990
 2009  no  3510
 2008  yes 900
 2008  no  3600
 ;
 run;

proc freq data = today;
 table year*yesno/chisq;
 weight count;
run;


Peter

Peter L. Flom, PhD
Statistical Consultant
www DOT peterflomconsulting DOT com
http://www.associatedcontent.com/user/582880/peter_flom.html