Re: teaching statistical methods by rules?

[Jerry Dallal]

Dale Berger wrote:
> 
> How about this one:  The sampling distribution of the mean is likely to be
> approximately normal with a sample of at least 30 cases IF the population is
> roughly symmetrical with no extreme outliers.   Diagnosis: Plot the data,
> plus use whatever information is available about the population
> distribution.
> 
> What do you think?
> 
> Cheers, Dale Berger
> 

That's essentially what I tell my students and back it up 
with pictures like those in Freedman, Pisani and Purves.
I hedge a little on the 30.  It's more like starting
to feel comfortable at 30, relaxed at 60, and not a
care in the world at 100, provided they (as has become
the class slogan), "Show me the data!"