David J Firth wrote:
>
> : You're running into a historical artifact: in pre-computer days, using the
> : normal distribution rather than the t distribution reduced the size of the
> : tables you had to work with. Nowadays, a computer can compute a t
> : probability just as easily as a z probability, so unless you're in the
> : rare situation Karl mentioned, there's no reason not to use a t test.
>
> Yet the old ways are still actively taught, even when classroom
> instruction assumes the use of computers.
The z test and interval do have some value as a pedagogical
scaffold with the better students who are intended to actually
_understand_ the t test at a mathematical level by the end of the
course.
For the rest, we - like construction crews - have to be careful
about leaving scaffolding unattended where youngsters might play on it
in a dangerous fashion.
One can also justify teaching advanced students about the Z test so
that they can read papers that are 50 years out of date. The fact that
some of those papers may have been written last year - or next- is,
however, unfortunate; and we should make it plain to *our* students that
this is a "deprecated feature included for reverse compatibility only".
-Robert Dawson
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