[R] sample mean, variance and SD

[David Winsemius]

On Nov 10, 2012, at 6:58 PM, Jim Lemon wrote:

> On 11/11/2012 07:09 AM, Greg Snow wrote:
>> This is to all R-helpers (Sarah is just the one that I am replying to),
>> 
>> Have we become a little too draconian on the "not a homework help list"
>> issue?
>> ...
> 
> As usual, a thoughtful comment on a problem that does not have a straightforward solution. The actual responses to obvious homework questions range from curt refusals to worked examples. I don't know the official status of the "no homework" policy if there is one.

The fourth entry (very close to the top)  in the Posting Guide says:
"<b>Basic statistics and classroom homework:</b> R-help is not intended for these."


> My responses are guided by their expected utility. If the question appears to be asked by someone who has just gotten stuck on an esoteric quirk of R (and the extraction operators are a good example), I'll try to get them over the hump.

That's been my approach as well.  I may simply offer:

?<func-name>

... but if they merely post an obvious homework problem with no effort visible I will either ignore it or point to the Posting Guide. Sometimes a preamble along the lines of "I tried to do this and cannot get academic support because the teacher is using SAS" will be sufficiently convincing. 

> In this particular case, parvez_200207 seems to have answered the question and not realized it.

I wondered whether parvez_200207 wanted to do the same procedure 1000 times and record the summary statistics each time. 

> Maybe this was due to something that parvez_200207 didn't even know was going on (e.g. a sink() was operating) or maybe it was just complete cluelessness. If I strongly suspected the former, I probably would have answered.
> 
-- 

David Winsemius, MD
Alameda, CA, USA