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

From   David Hoaglin <>
Subject   Re: st: Interpretation of Two-sample t test with equal variances?
Date   Wed, 20 Mar 2013 15:14:58 -0400

Thanks, Nick.

I was going to suggest a dotplot, but held off.  The sample sizes are
large enough that some jittering may be helpful.

Preferences for plots may vary, but a thorough analysis should include
graphical displays of the data.

David Hoaglin

On Wed, Mar 20, 2013 at 12:58 PM, Nick Cox <> wrote:
> I wouldn't want to start with box plots here. For two groups, there is
> space for more detail than a box plot gives, except capriciously in so
> far as points are more than 1.5 IQR from the nearer quartile.
> 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.
> I have often seen -- even in otherwise good textbooks -- people
> talking about t-tests or ANOVA and then giving box plots -- and not
> even commenting on the mismatch, i.e. that the box plots are showing
> medians etc., not means etc.
> A more directly relevant graph would, I suggest, be a dotplot (sensu
> -dotplot-) or even -stripplot- (SSC). You can show means on such
> plots.
> Nick
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