Re: Tests of "significance"

[samir-9]

---------------------------- Original Message ----------------------------
Subject: Re: Tests of "significance"
From:    [hidden email]
Date:    Tue, April 8, 2008 9:31 am
To:      [hidden email]
--------------------------------------------------------------------------

Dear Hector:

Just wondering abt one  point - how did u assume that the sample Bob is
working on is too small. He hasnt mentioned it yet. He has talked abt
neither the universe nor the sample.

I certainly aggree with your statement on small sample against a large
universe. But what if the sample is considerable sufficient and
representative?

Cant we say 'the variables have certain association in as many as 95%
cases' if the chi-square value comes out to be significant at .05 level
from the contigency table on the two variables he is concerned with.
Please put some more insights on it if i am not correct to any extent.

Regards,
Sam

> You could say that any difference observed might possibly be due to mere
> chance. You do not have sufficient grounds to affirm that a relationship
> or
> difference actually exists in the population, based on the relationship
> observed in your sample, because the observed difference or relationship
> is
> too weak for the size of your sample, or the size of your sample is too
> small for such a weak relationship. You need a larger sample, or a
> stronger
> relationship/difference, or both.
>
> Notice also that this concerns your ability to infer from your sample to
> the
> population, and has nothing to do with the substantive significance of
> your
> hypothesis. Even a very small (and thus substantively "insignificant")
> effect may be found to be statistically significant if the sample is
> sufficiently large.
>
> Hector
>
> -----Original Message-----
> From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of
> Bob
> Schacht
> Sent: 07 April 2008 23:09
> To: [hidden email]
> Subject: Tests of "significance"
>
> Please help me out here. The cautious, humble statistician says, "At the
> .05 level, the Null Hypothesis is rejected." To the man on the street,
> this
> is just pedantic mumbo-jumbo. So, say I'm using SPSS to do a Chi-square on
> responses to a Likert scale question by case outcome. If the Chi-square
> comes out with p< .05, I say, somewhat formally, "At the .05 level, the
> Null Hypothesis that case outcome and responses to this question are
> independent, is rejected."
>
> How can I translate that into plain English that the proverbial man on the
> street can understand, while remaining statistically correct?
>
> I am looking for a generic phrase that can be used for all similar
> statistical tests based on a null hypothesis of independence.
>
> Thanks,
> Bob
>
>
> Robert M. Schacht, Ph.D. <[hidden email]>
> Pacific Basin Rehabilitation Research & Training Center
> 1268 Young Street, Suite #204
> Research Center, University of Hawaii
> Honolulu, HI 96814
>
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