I used the word 'conservative' in the sense of avoiding basing judgements on belief rather than evidence as much as possible.
Alan McLean
On Sunday, November 24, 2002, at 11:29 AM, Radford Neal wrote:
In article <[EMAIL PROTECTED]>,
Alan McLean <[EMAIL PROTECTED]> wrote:
In practice the population is almost always a model - at best it is ill
defined. So the value of sigma is virtually never meaningfully 'known'.
At the same time, a role of statistical analysis is to save one from
jumping to unwarranted conclusions - so one should be conservative. On
this basis, it is preferable to use t even when you might think z is
reasonable.
But what if the sample standard deviation that you computed to do your
t test is substantially less than what you think sigma is? Is it really
"conservative" to ignore this, and quote a result that is based on what
you have reason to believe is an optimistic estimate of the accuracy of
the observations?
Radford Neal
