Posted by
Mike on
Apr 12, 2011; 12:47pm
URL: http://spssx-discussion.165.s1.nabble.com/p-value-type-I-error-tp4296382p4298118.html
----- Original Message -----
From: "drfg2008" <
[hidden email]>
>
> If I for example compute a t-Test and get as a result (let’s say) p=0,0123
> I would reject the H0 since p < 0,05. The result is considered
> ‘statistically significant’. So far so good. However, what about the type I
> error. Is the type I error 0,0123 ?
If the null hypotheis is true, any statistical test with p< .05 is a
Type I error because such a result would lead to the false rejection
of a true null hypothesis.
If the null hypothesis is false, it is a correct rejection of the null
hypothesis (if one has set alpha=0.05, that is, how extreme should
a result be for one to use it as evidence against the null hypothesis).
If the null hypothesis is false, there is no Type I error (though one
could screw up in other ways).
The problem is in real life research we don't really know if the
null hypothesis is true or not (though some may hold different
opinions about this). Through replication of the original result,
the probability that a whole series of statistically significant
results are all Type I errors becomes extremely small.
-Mike Palij
New York University
[hidden email]
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