Posted by
statisticsdoc on
Dec 19, 2006; 1:16pm
URL: http://spssx-discussion.165.s1.nabble.com/Significant-difference-Means-tp1072801p1072814.html
Hi Jan and John,
Jan is correct. With the information that Samir possesses, formally one
should test the null hypothesis that the two samples have the same mean,
which is accomplished by using the independent groups t-test. Samir does
not possess information about the population mean. The mean of a sample of
1,000 is merely an estimate of the population mean - it is a statistic, not
a parameter.
Regards to All,
Stephen Brand
For personalized and professional consultation in statistics and research
design, visit
www.statisticsdoc.com
-----Original Message-----
From: SPSSX(r) Discussion [mailto:
[hidden email]]On Behalf Of
Spousta Jan
Sent: Tuesday, December 19, 2006 3:54 AM
To:
[hidden email]
Subject: Re: Significant difference - Means
Hi John, the error of that 3.5 is about sqrt(1/1000) = 0,03 while the error
of 2.9 for students is about sqrt(1/500) = 0.045. That is both errors are of
the same order of magnitude and the population error cannot be neglected in
this case.
Merry Christmas,
Jan
-----Original Message-----
From: SPSSX(r) Discussion [mailto:
[hidden email]] On Behalf Of
John Antonakis
Sent: Tuesday, December 19, 2006 9:46 AM
To:
[hidden email]
Subject: Re: Significant difference - Means
Hi Jan:
I agree that the 3.5 is not a perfect measure. However, If Samir believes
that 3.5 represents the population mean (with a sample of 1,000 the standard
error should be very small) then that is precisely the case in which one
would use the single-sample test.
If he just wants to compare the means of the two groups then I agree that
the independent sample t-test is more appropriate (because it takes into
account the standard error of the population mean).
Regards,
John
At 09:30 19.12.2006 +0100, Spousta Jan wrote:
>I am very sorry, but this would be wrong in this case. Because the
>number
>3.5 is not a constant known with (almost) no error, but a sample
>statistics based on the 1000 respondents. Therefore the
>Independent-samples T-test should be used as I've written in my
>previous posting.
>
>Jan
>
>-----Original Message-----
>From: SPSSX(r) Discussion [mailto:
[hidden email]] On Behalf
>Of John Antonakis
>Sent: Tuesday, December 19, 2006 9:25 AM
>To:
[hidden email]
>Subject: Re: Significant difference - Means
>
>If you wiysh to test the mean of a particular group against the mean of
>a particular value then you can use the single-sample t-test (from the
>Menus Analyze/Compare Means/One sample t-test), or use the syntax:
>
>T-TEST
> /TESTVAL = 3.5
> /MISSING = ANALYSIS
> /VARIABLES = VAR00001
> /CRITERIA = CI(.95) .
>
>HTH,
>J.
>
>At 09:05 19.12.2006 +0100, =?iso-8859-2?Q?Samir_Omerovi=E6?= wrote:
> >Hi to all,
> >
> >
> >
> >My first question is what test should I use if I need to assess the
> >significance of the mean of some subgroup in comparison the mean of
> >the total population. For example I have 1000 respondents that
> >answered a question on 7-point scale. Their mean/average is 3,5. I
> >have 500 students among those 1000 respondents with mean/average 2,9.
> >I want to know if these values are significantly different.
> >What test should I use in SPSS?
> >
> >
> >
> >Thanks to all in advance.
> >
> >
> >
> >Samir
> >
> >
> >
> >GfK BH
> >
> >Centar za istrazivanje trzista i javnog mnijenja d.o.o.
> >
> >
> >
> >Samir Omeroviæ
> >
> >Researcher
> >
> >
> >
> >71 000 Sarajevo, Skenderija 44
> >
> >Bosna i Hercegovina
> >
> >
> >
> >
> >
> >Tel: +387 33 550 300
> >
> >Fax: +387 33 444 226
> >
> >www.gfk.ba
> >
> >www.gfk.com
> >
> >
> >
> >
> >
> >
> >
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>___________________________________
>
>Prof. John Antonakis
>Faculty of Management and Economics
>University of Lausanne
>Internef #527
>CH-1015 Lausanne-Dorigny
>Switzerland
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>Tel: ++41 (0)21 692-3438
>Fax: ++41 (0)21 692-3305
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http://www.hec.unil.ch/jantonakis>___________________________________
___________________________________
Prof. John Antonakis
Faculty of Management and Economics
University of Lausanne
Internef #527
CH-1015 Lausanne-Dorigny
Switzerland
Tel: ++41 (0)21 692-3438
Fax: ++41 (0)21 692-3305
http://www.hec.unil.ch/jantonakis___________________________________