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Re: st: Interpretation of Two-sample t test with equal variances?


From   David Hoaglin <dchoaglin@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Interpretation of Two-sample t test with equal variances?
Date   Wed, 20 Mar 2013 15:22:26 -0400

Jay,

I'm not aware that boxplots make any assumptions.  They show what they
are intended to show.  Their "performance" comes from the way people
interpret them.  Boxplots of skewed data will tend to have certain
characteristics, boxplots of light-tailed data will have other
characteristics, and so on.  Some patterns suggest bimodal data.

David Hoaglin

On Wed, Mar 20, 2013 at 2:56 PM, JVerkuilen (Gmail)
<jvverkuilen@gmail.com> wrote:
> On Wed, Mar 20, 2013 at 12:58 PM, Nick Cox <njcoxstata@gmail.com> wrote:
>>
>> I grew up, as it were, on box plots, including David's own writings 30
>> or more years ago, but I think they are oversold in total.
>
> Yes, boxplots are really great in many circumstances, but they have
> some built in assumptions, such as unimodality of the distribution,
> and in general perform poorly when you have a light-tailed
> distribution. I doubt that's the case here, but with only two groups
> it's possible to do a lot more.
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