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RE: st: Sampling for proportion: characteristic of interest
From
"Ilian, Henry (ACS)" <[email protected]>
To
"'[email protected]'" <[email protected]>
Subject
RE: st: Sampling for proportion: characteristic of interest
Date
Fri, 24 Aug 2012 15:11:17 -0400
Stas, thank you.
The question was: when you need to specify a proportion to calculate a sample size, the proportion is of a characteristic of interest, but when you have several characteristics of interest, all of which are important, how do you specify the proportion.
Your answer would suggest that if there are yes/no questions on the instrument, then I need to specify 50% and therefore use a larger sample size. When you say you specify 10%-20% for Likert/multinomial scales, what percentage do you use for the calculation?
Henry
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Stas Kolenikov
Sent: Friday, August 24, 2012 2:58 PM
To: [email protected]
Subject: Re: st: Sampling for proportion: characteristic of interest
What exactly is your question here? You have not really stated what do
you want to determine. You don't seem to have much of a design/sample
size issue here, if you are set on sampling a known number of cases.
When I write study precision and power sections, I usually specify
several levels of incidence -- e.g., 10%, 20% and 50%. The 50% would
be relevant for the Yes/No answers on your instrument; the 10%-20%
would be relevant for your Likert/multinomial scales.
--
-- Stas Kolenikov :: http://stas.kolenikov.name
-- Senior Survey Statistician, Abt SRBI :: work email kolenikovs at
srbi dot com
-- Opinions stated in this email are mine only, and do not reflect the
position of my employer
On Fri, Aug 24, 2012 at 11:35 AM, Ilian, Henry (ACS)
<[email protected]> wrote:
> I need to take a quality-control sample for a case-reading study. A random sample of about 600 cases will be drawn and read, and I need a sample of those to be read by a second reader. The case-reading instrument has approximately 100 questions--the final number hasn't been determined yet. The response choices mostly form ordinal scales, although a few will be nominal, hence I'll be sampling for proportion.
>
> Everything I can find on sampling for proportion only considers the proportions for a single characteristic of interest. I have 100+ characteristics with different expected proportions. How do I approach this problem?
>
> Many thanks,
>
> Henry Ilian
>
>
>
>
>
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