LISTSERV at the University of Georgia
Menubar Imagemap
Home Browse Manage Request Manuals Register
Previous messageNext messagePrevious in topicNext in topicPrevious by same authorNext by same authorPrevious page (October 2002)Back to main SPSSX-L pageJoin or leave SPSSX-L (or change settings)ReplyPost a new messageSearchProportional fontNon-proportional font
Date:         Wed, 9 Oct 2002 18:09:38 -0500
Reply-To:     Jelani Mandara <jelani@citrus.ucr.edu>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         Jelani Mandara <jelani@citrus.ucr.edu>
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: http://www.sesp.northwestern.edu/people/sp/j_mandara.html > > >

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

Office Phone: (847)491-3122 Web Page: http://www.sesp.northwestern.edu/people/sp/j_mandara.html


Back to: Top of message | Previous page | Main SPSSX-L page