# [R] Testing the equality of two variances

R. Michael Weylandt michael.weylandt at gmail.com
Mon Oct 22 15:19:47 CEST 2012

```Hi Tammy,

I'm afraid this is pretty obviously homework, so we can't really do
much to help you. It's not a personal thing: just the considered
opinion of this list to believe that giving you answers (or even hefty
hints) may undermine whatever intent your teacher has in assigning the
problem. There are a good number of us in education of one form or
another who wouldn't appreciate having that done, so it's really just
professional courtesy.

I can direct you to the help manuals that ship with R, however: simply
type help.start() at the prompt and you will be given a good suite of
options.

Cheers,
Michael

On Mon, Oct 22, 2012 at 12:08 PM, Tammy Ma <metal_licaling at live.com> wrote:
>
> Dear R-User,
>
> I met the problem to test equality of variance.
>
> Two sample units:
> conjps<-c(9.41,10.45,10.78,10.73,11.11,11.12,11.59,11.04,11.63)
>
> ms<-c(4.11,5.10,5.70,6.46,6.04,6.16, 6.24,6.32,7.33)
>
> Then I use the F test to test:
>
>
>
> 謬est Equality
> of
> Two Variances
>
>  F
> test to compare two variances
>
>
>
> data:
> conjps and ms
>
> F = 0.5419, num df = 8,
> denom df = 8,
> p-value = 0.4045
>
> alternative hypothesis: true ratio of
> variances is not equal to 1
>
> 95 percent confidence interval:
>
>  0.1222368 2.4024170
>
> sample estimates:
>
> ratio of variances
>
>
> 0.5419076
>
>
> but If conjps is replaced by conjps1: shifting the first value and the last value position
> conjps1<-c(11.36,10.45,10.78,10.73,11.11,11.12,11.59,11.04,9.41)
>
> I do believe we get the same result when testing the equity of variance. but how do I distringuish this two cases by testing?
> Kind regards,Tammy
>
>
>
>
>         [[alternative HTML version deleted]]
>
>
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