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Re: st: sign test output
From
Nick Cox <[email protected]>
To
[email protected]
Subject
Re: st: sign test output
Date
Thu, 17 Jan 2013 12:22:37 +0000
The row boat [English English: rowing boat] joke is as least as old as
a comment in
Box. G. E. P. 1953. Non-normality and tests on variances. Biometrika 40: 318-35
which is otherwise germane to the discussion in several ways, not
least in introducing the term "robustness".
Nick
On Thu, Jan 17, 2013 at 12:14 PM, Maarten Buis <[email protected]> wrote:
> On Thu, Jan 17, 2013 at 11:21 AM, Nahla Betelmal wrote:
>> from my readings in statistics , I know that in order to decide
>> whether to use parametric or non-parametric tests, the data normality
>> distribution should be checked first.
>>
>> Shapiro-Wilk is used to test normality, when the number of
>> observations is less than 30. Otherwise, we should use
>> Kolmogorov-Smirnov for large sample (as in my sample).
>
> Unfortunately that is incorrect. Normality tests need huge samples
> before the p-value means what it is supposed to mean. An analogy I
> have heard in a different context, but which applies to this situation
> very well is: to go out to sea in a row boat to check whether the sea
> is safe for the QE II.
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