On 19 Apr 2001 05:26:25 -0700, [EMAIL PROTECTED] (Robert J.
MacG. Dawson) wrote:
[ ... ]
> 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 that they can read papers that are 50 years out of date.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".
Mainly, I disagree.
I had read 3 or 4 statistic books and used several stat programs
before I enrolled in graduate courses. One of the *big surprises* to
me was to learn that some statistics were approximations,
through-and-through, whereas others might be 'exact' in some sense.
Using z as the large sample test, in place of t, is approximate.
Using z as the test-statistic on a dichotomy or ranks is exact, since
the variances are known from the marginal Ns.
Using z for *huge* N is a desirable simplifications, now and then.
Is the 1-df chi-squared equally worthless, in your opinion?
A lot of those exist, fundamentally, as the square of a z that
*could* be used instead (for example, McNemar's test).
--
Rich Ulrich, [EMAIL PROTECTED]
http://www.pitt.edu/~wpilib/index.html
=================================================================
Instructions for joining and leaving this list and remarks about
the problem of INAPPROPRIATE MESSAGES are available at
http://jse.stat.ncsu.edu/
=================================================================
