[SciPy-Dev] Resolving PR 235: t-statistic = 0/0 case

Nathaniel Smith njs@pobox....
Thu Jun 7 15:13:31 CDT 2012


On Thu, Jun 7, 2012 at 5:29 AM, Junkshops <junkshops@gmail.com> wrote:
> - I'll merge the two 2 sample t-test functions
> - add an uneq_var=False kw arg, setting to true will use the new code

equal_var would be a better name, to avoid the double-negative.

Would it be possible/desireable to make equal_var=False the default?
Obviously this would require a deprecation period, but as semantic
changes go it's relatively low risk -- anyone who misses the warnings
etc. would just find one day that their t tests were producing more
conservative/realistic values.

(R defaults to doing the unequal variances test, and I have actually
seen this fact used in their advocacy, as evidence for their branding
as the tool for people who care about statistical rigor and
soundness.)

> - add an zoz=np.nan kw arg and a check that it's np.nan, 0 or 1.
> Otherwise raise ValueError

Let's please not add this "zoz=" feature. Adding features has a real
cost (in terms of testing, writing docs, maintenance, and most
importantly, the total time spent by all users reading about this
pointless thing in the docs and being distracted by it). It's only
benefit would be to smooth over this debate on the mailing list; I
can't believe that any real user will actually care about this, ever.

(And if such a user ever does show up, then adding a feature is an
easy backwards-compatible change; removing it isn't.)

> - update docs & tests.
> - push.

-n


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