Date:         Mon, 1 Apr 2002 13:54:50 -0500
Reply-To:     Larry Kaskey <LKaskey@TRACFONE.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Larry Kaskey <LKaskey@TRACFONE.COM>
Subject:      Re: Chi Square interpretation
Content-Type: text/plain; charset="iso-8859-1"

Thanks Peter, but I thought, perhaps wrongly, that a t-test would work for
continuous data, such as comparing the time it takes for a person to redeem
the coupon, where a chi square would be better for catagorical data such as
in my case, response or no response.

My statistics is very rusty so I am easily influenced!

Thanks for the help,

Larry Kaskey
Retention Analyst
305-418-2412

-----Original Message-----
From: Peter Flom [mailto:flom@NDRI.ORG]
Sent: Monday, April 01, 2002 1:43 PM
To: SAS-L@LISTSERV.UGA.EDU
Subject: Re: Chi Square interpretation


One question is why do Chi-sqare rather than a t-test?

You have two samples, and a proportion from each who did something.

And you can then get a confidence interval around the difference.

However, on the data you gave, it seems to me like your conclusion is
correct.  It just might be a type 3 error - solving the wrong problem

The other big question is, whether or not any test is significant or not,
you care, on a substantive level, about the difference in the two rates.
Even if 6.9% and 6.4% are exactly the right values, would you want to go
ahead?

HTH



Peter L. Flom, PhD
Assistant Director, Statistics and Data Analysis Core
Center for Drug Use and HIV Research
National Development and Research Institutes
71 W. 23rd St
New York, NY 10010
(212) 845-4485 (voice)
(917) 438-0894 (fax)