besides, who needs those tables? we have computers now, don't we?
I was told that there were tables for logarithms once. I have not seen one
in my life. Is not it the same kind of stuff?
>
> 3. Outdated.
>
> on the grounds that when sigma is unknown, the proper distribution is t
> (unless N is small and the parent population is screwy) regardless how
> large the sample size may be. The main (if not the only) reason for the
> apparent logical bifurcation at N = 30 or thereabouts was that, when
> one's only sources of information about critical values were printed
> tables, 30 lines was about what fit on one page (plus maybe a few extra
> lines for 40, 60, 120 d.f.) and one could not (or at any rate did not)
> expect one's business students to have convenient access to more
> extensive tables of the t distribution. And, one suspects latterly,
> authors were skeptical that students would pay attention to (or perhaps
> be able to master?) the technique of interpolating by reciprocals between
> 30 df and larger numbers of df (particularly including infinity).
>
> But currently, _I_ would not expect business students to carry out the
> calculations for hypothesis tests, or confidence intervals, by hand,
> except maybe half a dozen times in class for the good of their souls:
> I'd expect them to learn to invoke a statistical package, or else
> something like Excel that pretends to supply adequate statistical
> routines. And for all the packages I know of, there is a built-in
> function for calculating, or approximating, the cumulative distribution
> of t for ANY number of df. The advice in any _current_ business-
> statistics text ought to be, therefore, to use t _whenever_ sigma is not
> known. And if the textbook isn't up to that standard, the instructor
> jolly well should be.
>
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