[R] sample mean, variance and SD

[Berend Hasselman]

On 10-11-2012, at 21:09, 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?

Probably.

> 
> Now if someone just states the HW question, gives no indication that they
> have done anything to try to solve it themselves, and expects us to give
> them a completed answer without effort on their part, I am happy to light
> up the flame thrower (and if they are my students they could very well lose
> points for poor questions).  But I think there are cases where it is
> reasonable for us to help point students in the right direction (at our
> own discretion, but without a knee jerk "no homework" response).  Some of
> the types of questions that we have seen on this list that I think would
> qualify here would include things like:
> 
> I already turned in my homework after using <program other than R> that the
> teacher uses, but now I would like to learn how to do it in R as well, can
> anyone give me pointers to which help page(s) I should read to learn how to
> do <topic>.
> 
> My teacher says we can use any program we want and I chose R, but the
> teacher and TA's don't know R, I have figured out most of this problem
> <problem statement and code tried so far>, but I can't figure out how to do
> this last part, any pointers?
> 
> I fit this model <model info> to the HW data using <R commands> and these
> are the results that I see <results>, but the answer in the book while
> matching on some things has a different value for these coefficients <list
> with other numbers>.  I am thinking that R must be using a different
> default or encoding than the book, can anyone explain the reason for the
> difference or give a pointer to where it is documented?
> 
> And other cases where a student is clearly doing homework, but shows that
> they have made an effort on their own and is not demanding we do the work
> for them, but would rather like a pointer or hint to help them learn
> better.  I vote that we adopt a policy (unofficial) that if a student shows
> effort and asks a reasonable question that we respond with answers that
> will help the student continue to learn (and become a better member of the
> R community).  What do others think?
> 

I would tend to agree with the last paragraph.


Berend


> 
> On Sat, Nov 10, 2012 at 11:40 AM, Sarah Goslee <sarah.goslee at gmail.com>wrote:
> 
>> This is not a homework help list.
>> 
>> On Saturday, November 10, 2012, parvez_200207 wrote:
>> 
>>> hi
>>> could you help me to solve this issue
>>> 
>>> Question:
>>> Using command rweibull(100,8,15), simulate n = 100 realizations from
>>> Weibull(8; 15) distribution. Using the simulated sample, compute the
>> sample
>>> mean, variance and standard deviation of these observations.
>>> 
>>> I am trying like this
>>> 
>>> sim<-rweibull(100,8,15) # simulated sample
>>> SM<-mean(sim) # simulated sample mean
>>> var(sim)      # variance
>>> sd(sim)       #SD
>>> 
>>> Thank you in advance.
>>> 
>>> Parvez
>>> 
>>> 
>>> 
>>> --
>>> View this message in context:
>>> http://r.789695.n4.nabble.com/sample-mean-variance-and-SD-tp4649190.html
>>> Sent from the R help mailing list archive at Nabble.com.
>>> 
>>> ______________________________________________
>>> R-help at r-project.org <javascript:;> mailing list
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>>> PLEASE do read the posting guide
>>> http://www.R-project.org/posting-guide.html
>>> and provide commented, minimal, self-contained, reproducible code.
>>> 
>> 
>> 
>> --
>> Sarah Goslee
>> http://www.stringpage.com
>> http://www.sarahgoslee.com
>> http://www.functionaldiversity.org
>> 
>>        [[alternative HTML version deleted]]
>> 
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>> 
> 
> 
> 
> -- 
> Gregory (Greg) L. Snow Ph.D.
> 538280 at gmail.com
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.