[Rd] Return/print standard error in t.test()

[Thomas J. Leeper]

Hi John,

Thanks for your reply. Of course I could write a package and of course I
would find that trivial to do. The point is this is a main entry point to R
for probably (at this point) hundreds of thousands of students. I’d like
them to be able to get a basic quantity of interest from a t-test without
four subsequent function calls.

I also don’t really see the point about the object class, given we’re
talking S3. print() doesn’t have to print everything in the object (see
e.g., print.lm() ), so there should be little harm in returning additional
information when relevant. Leaving the print() method unchanged and simply
returning the SE as an additional element should affect almost nothing.

I’m all for continuity and conservative development, but we also should aim
to make R as useful and usable as possible. This seems like a nice simple
way to do that.

Best,
Thomas


On Thu, 21 Feb 2019 at 21:51 Fox, John <jfox using mcmaster.ca> wrote:

> Dear Thomas,
>
> it is, unfortunately, not that simple. t.test() returns an object of class
> "htest" and not all such objects have standard errors. I'm not entirely
> sure what the point is since it's easy to compute the standard error of the
> difference from the information in the object (adapting an example from
> ?t.test):
>
> > (res <- t.test(1:10, y = c(7:20)))
>
>         Welch Two Sample t-test
>
> data:  1:10 and c(7:20)
> t = -5.4349, df = 21.982, p-value = 1.855e-05
> alternative hypothesis: true difference in means is not equal to 0
> 95 percent confidence interval:
>  -11.052802  -4.947198
> sample estimates:
> mean of x mean of y
>       5.5      13.5
>
> > as.vector(abs(diff(res$estimate)/res$statistic)) # SE
> [1] 1.47196
> > class(res)
> [1] "htest"
>
> and if you really want to print the SE as a matter of course, you could
> always write your own wrapper for t.test() that returns an object of class,
> say, "t.test" for which you can provide a print() method. Much of the
> advantage of working in a statistical computing environment like R (or
> Stata, for that matter) is that you can make things work the way you like.
>
> Best,
>  John
>
>   -------------------------------------------------
>   John Fox, Professor Emeritus
>   McMaster University
>   Hamilton, Ontario, Canada
>   Web: http::/socserv.mcmaster.ca/jfox
>
> > On Feb 21, 2019, at 3:57 PM, Thomas J. Leeper <thosjleeper using gmail.com>
> wrote:
> >
> > A recent thread on Twitter [1] by a Stata user highlighted that t.test()
> > does not return or print the standard error of the mean difference,
> despite
> > it being calculated by the function.
> >
> > I know this isn’t the kind of change that’s likely to be made but could
> we
> > at least return the SE even if the print() method isn’t updated? Or,
> > better, update the print() method to display this as well?
> >
> > Best,
> > Thomas
> >
> > [1]
> > https://twitter.com/amandayagan/status/1098314654470819840?s=21
> > --
> >
> > Thomas J. Leeper
> > http://www.thomasleeper.com
> >
> >       [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-devel using r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-devel
>
> --

Thomas J. Leeper
http://www.thomasleeper.com

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