> Ok, thanks to Nick Winters, I have learned something new
By the way, it is "Winter" -- no "s" -- a pet peeve of mine.
> Warning: Since ttest is not an estimation command or does
> not set e(sample), bs has no way to determine
> which observations are used in calculating the
> statistics and so assumes that all observations
> are used. This means no observations will be
> excluded from the resampling due to missing values
> or other reasons.
> If the assumption is not true, press Break, save
> the data, and drop the observations that are to
> be excluded. Be sure the dataset in memory
> contains only the relevant data.
On the substance, the warning means that you must ensure there are no
missing observations on your diff variable. You can do this by typing
. count if diff==.
If there are any, you should drop those observations before running your
bootstrap:
. preserve
. drop if diff==.
<<run bootstrap>>
. restore
By the way, you could just use the -summarize- command, rather than the
-ttest-, if all you want is the mean.
Nick Winter
*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
