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Date:         Wed, 9 Oct 2002 18:09:38 -0500
Reply-To:     Jelani Mandara <>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         Jelani Mandara <>
Subject:      Re: Sample vs Population
Content-Type: text/plain; charset=windows-1252; format=flowed

Alison Neustrom wrote:

>What would you say if you had 80% of a non-random sample of a population (I >sent them to everyone but only got back 80%)? Would you consider that a >sample or a population? > > >

Inferential stats rely on the size of the sample more than the % of the population sampled. This is a weakness, but since we rarely know the actual size of the population, it's understandable.

So, I would argue that it depends on the size of the sample/population. If you have 80% of 100, then you may wish to increase alpha, since you risk the chance of Type II errors (i.e., incorrectly concluding a null result). I think increasing alpha will be more reliable than just using descriptives to test nulls in small samples when you have 80% of the population. In large samples (say, N > 1000) I doubt it matters. Some of the statisticians on the list may know for sure.

>-----Original Message----- >From: SPSSX(r) Discussion [mailto:SPSSX-L@LISTSERV.UGA.EDU]On Behalf Of >Jelani Mandara >Sent: Wednesday, October 09, 2002 11:50 AM >To: SPSSX-L@LISTSERV.UGA.EDU >Subject: Re: Sample vs Population > > >Fink, Steven wrote: > > > >>Recently, I've been asked by several analysts about analyzing populations, >> >> >that is, data not from a sample. > > >>The purpose of a statistical test is to make estimates about the >> >> >population. If my data set IS the population, are significant tests >appropriate? > > >> >> >> >No. Descriptives and Effect Sizes are still relevant, but not >inferential stats. > > > >>What about if my response rate (survey/unit) is low, say 20%. For example, >> >> >I sent surveys to everyone in the population, but only received 20% of >responses. Does this change your answer to the first question? > > >> >> >> >> > >Then you only have a (probably nonrandom) sample of the population. The >logic of inferential stats applies. > > > >>Thanks >> >> >> >>Steve >> >> >> >> >> > >-- >Jelani Mandara >Assistant Professor >Human Development and Social Policy >Northwestern University >2120 Campus Drive >Evanston, Il 60208 > >Office Phone: (847)491-3122 >Web Page: > > >

-- Jelani Mandara Assistant Professor Human Development and Social Policy Northwestern University 2120 Campus Drive Evanston, Il 60208

Office Phone: (847)491-3122 Web Page:

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