Date:         Fri, 20 Dec 2002 16:53:53 -0800
Reply-To:     Cassell.David@EPAMAIL.EPA.GOV
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         "David L. Cassell" <Cassell.David@EPAMAIL.EPA.GOV>
Subject:      Re: help on power analysis
Content-type: text/plain; charset=us-ascii

Steve Albert <salbert@AOL.COM> replied [in part]:
> sampling theory here.  You need to understand the sampling design, and
the
> issues involved.  (You also haven't described how your health care
workers
> are to be recruited, which may introduce some biases of its own, or
how
> they're told to select the n individuals from their communities, which
may
> introduce other biases, affect the correlation between observations in
each
> cluster, etc.)

Exactly.  The OP is going to have a host of potential problems
with response errors and non-response errors.  So a large part
of the process of designing the study is likely to be the design
of the *logistics* involved, so the fieldwork produces the design
that the statisticians planned.

> 185.  A more mathematical treatment is in William Cochran's "Sampling
> Techniques", 3rd edition (a classic on sampling),

Cochran's book also has a list of the 11 steps involved in the
process of sampling.  I have just written about this in an invited
paper I'll be doing at SUGI with AnnMaria de Mars (Rousey).  I have
found more than one study where a good statistical design was ruined by
poor logistical planning and implementation.  So the OP really needs to
talk with people who have experience *implementing* sampling designs.

The American Statistical Association has a short series of pamphlets
whch might be helpful for the beginner.  They are written for the
general public, and are produced by:

Section on Survey Research Methods
American Statistical Association
1429 Duke St.
Alexandria, VA, USA
zipcode 22314-3402

The titles I know of are:

"What is a survey?"

"How to plan a survey"

"How to Collect survey data"

"What are the main sources of survey error?"

"What about surveys in the media?"


BTW, some of the authors on these are Westat folks.

David
--
David Cassell, CSC
Cassell.David@epa.gov
Senior computing specialist
mathematical statistician