That is fair enough, Robert, but the original question was about a lack of
statistical significance.
Martin
On 25 July 2018 at 12:40, Robert Newcombe <[log in to unmask]> wrote:
> In answer to Martin's comment - it is true that in terms of achieving
> p<0.05, a non-parametric correlation measure is useless here. Nevertheless,
> my stance is that quantities such as correlation coefficients, odds ratios,
> etc. etc., should be regarded primarily as measures of effect size - which
> are sample-size-free and can be interpreted as point estimates - rather
> than as a route to obtaining a p-value.
>
>
>
> -----Original Message-----
> From: A UK-based worldwide e-mail broadcast system mailing list [mailto:
> [log in to unmask]] On Behalf Of Steve Nyangoma
> Sent: 25 July 2018 11:50
> To: [log in to unmask]
> Subject: Re: correlation coefficient
>
> Could resampling methods be used to generate more data to confirm evidence?
>
>
> On Wed, Jul 25, 2018 at 10:08 AM Martin Bland < 000017e8e212eb29-dmarc-
> [log in to unmask]> wrote:
>
> > Non-parametric is useless here, as with fewer than 6 observations all
> > possible values of either Spearman's or Kendall's have P>0.05.
> >
> > This is a case where the question of whether there is good evidence of
> > a relationship between two variables with only 4 observations always
> > has the answer "no, you would need more data."
> >
> > Martin
> >
>
> > On 25 July 2018 at 06:24, Juanita Hatcher <[log in to unmask]>
> > wrote:
> >
> > > I agree. Non parametric may be better, but one is still very
> > > restricted
> > by
> > > a very small data set. Look at the data.
> > >
> > > Juanita Hatcher
> > >
>
> > > > On Jul 24, 2018, at 2:33 PM, Robert Newcombe
> > > > <[log in to unmask]>
> > > wrote:
> > > >
> > > > Exactly! The first step is to plot a scatter diagram. Also, on a
> > dataset
> > > as small as this, there is no real positive assurance that
> > > parametric assumptions hold, and the correlation is particularly
> > > sensitive to distributional assumptions. So I suggest a
> > > non-parametric correlation rather than a parametric one anyway. With
> > > the proviso that this could
> > well
> > > be exactly 1, without this finding being anything to get excited about.
> > > >
> > > > Robert Newcombe.
> > > >
> > > >
> > > > -----Original Message-----
> > > > From: A UK-based worldwide e-mail broadcast system mailing list
> > [mailto:
> > > [log in to unmask]] On Behalf Of John Bibby
> > > > Sent: 24 July 2018 21:28
> > > > To: [log in to unmask]
> > > > Subject: Re: correlation coefficient
> > > >
> > > > Please look at the data, not the summary statistics. JOHN BIBBY
> > > >
> > > > On Tue, 24 Jul 2018 at 20:01, Martin Bland <
> > > > 000017e8e212eb29-dmarc-
> > > [log in to unmask]> wrote:
> > > >
> > > >> You are correct, the value of the correlation coefficient which
> > > >> would be significant with 4 observations is 0.95.
> > > >>
> > > >> Martin
> > > >>
> > > >> On 24 July 2018 at 17:57, paaveen jeyaganth <[log in to unmask]>
> > wrote:
> > > >>
> > > >>> Dear allstat ,
> > > >>> i have 4 data point i did a pearson correlation end up with r=
> > > >>> 0.8919 p= 0.1081 why is that it's not significant since it's
> > > >>> high correlation 0.89 because of sample size??
> > > >>>
> > > >>> Thanks
> > > >>> Paaveen
> > > >>>
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J. Martin Bland
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Dept. of Health Sciences
Seebohm Rowntree Building
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Heslington
York YO10 5DD
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Phone: 01904 321334 Fax: 01904 321382
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