# RE: st: RE: joint significant

 From "Nick Cox" <[email protected]> To <[email protected]> Subject RE: st: RE: joint significant Date Wed, 17 Jan 2007 09:57:12 -0000

```I would go a little further and warn you against
mixing confidence and significance terminology.

This practice presumably arises from noting instances
in which a result significant at the 5% level (say)
corresponds to one lying outside a 95% confidence interval,
but it does not really help anyone if one uses expressions
such as `significant at the 95% confidence level' (I quote here
from a statistics for Earth scientists book put out by a major
publisher).

There are several good reasons to avoid this usage completely.

First, there are significance tests not associated with a
confidence interval procedure.

Second, it will seem at best sloppy and at worst wrong to those
familiar with standard usage.

Third, it is one step down a slippery slope. The same book
makes frequent reference to significance at the 95% level
and alternates between talking of the 5% confidence level
and the 5% significance level. Competent statistical scientists
can decode what the author really means, but they should not
have to. Others can justifiably feel confused.

Naturally these are sins of my unnamed author (I will supply
the reference if anyone needs it!), but they are quoted to
emphasise the dangers here.

Nick
[email protected]

Rajesh Tharyan

> Let me rephrase what Justin has said...
>
> 1. The null hypothesis is the hypothesis you are testing for possible
> rejection under the assumption that it is true.
>
> 2. Therefore, you have to be concerned with wrongly rejecting
> something that
> you assume is true.
>
> 3. The maximum error you are willing to accept is say .05 i.e
> 5 out of 100
> (assuming 95% confidence = 5% significance that is where the
> .05 comes from)
>
> 4. The P value tell you what the significance level is. In
> .08 This is higher than what you are willing to accept.
>
> 5. Therefore there is not evidence statistically to reject
> what you assumed
> was true that is to repeat justins statement
>
> Based on a confidence level of 95%, I would fail to reject the null
> hypothesis that the estimated coefficients are jointly equal to zero.

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