|Date: ||Wed, 7 Apr 1999 09:04:21 -0400|
|Reply-To: ||Scott Dittloff <dittloff@CORNING-CC.EDU>|
|Sender: ||"SPSSX(r) Discussion" <SPSSX-L@UGA.CC.UGA.EDU>|
|From: ||Scott Dittloff <dittloff@CORNING-CC.EDU>|
|Subject: ||Re: Determining Population Size|
The issue isn't really about percentage of the population. Theoretically,
a sample of 2,000 will give you the same level of confidence in your
results for a population of 5,000 or 5,000,000 (provided that the sample
can be assumed to be normally distributed, etc.). The issue, for most
researchers is cost. A random sample of approximately 2,000 will give you
a confidence level of about 95%. Larger samples will increase the level of
confidence, but it will take many more cases to increase the confidence
level even one percent, and that costs more money.
From: Michele Atkinson [SMTP:matkinson@DELTATRENDS.COM]
Sent: Tuesday, April 06, 1999 8:58 PM
Subject: Determining Population Size
I'm pretty sure this isn't quite SPSS related but it definitely has a
statistical flavor to it, so bare with me :) I am wondering how to go about
determining what sample size I will need in order to fall into a 95%
confidence interval. There are approximately 20,000 stores we could survey.
We would like to take a sample of those stores to get an approximation of
the mean of the entire population. How do I go about deciding what
percentage of the total population I should survey in order to be confident
that the sample mean is a good estimation of the population mean? Please
let me know if I am being unclear or if more information is needed.
Have a great day and thanks!