[R] resampling problem counting number of means above a specific value

[Graham Smith]

David,

Thanks, its me getting mixed up I actually meant less than or equal to
10.  That apart, I guess the code is OK, I just expected, especially
as I increased N that I might have got some means less than 10, but
having gone back to it , I see I need a million iterations before
getting two means less than 10.

It seems I misjudged the probabilities.

Thanks again.

Graham



2009/11/15 David Winsemius <dwinsemius at comcast.net>:
>
> On Nov 15, 2009, at 12:12 PM, Graham Smith wrote:
>
>> I am trying to modify some code from Good 2005.
>>
>> I am trying  to resample the mean of 8 values and then count how many
>> times the resampled mean is greater than 10. But my count of means
>> above 10 is coming out as zero, which I know isn't correct.
>
> If that is your goal, then why are you using "<=" and not ">" in your test?
>
>> for(i in 1:N){
> +  LLb <- sample (LL, n, replace=TRUE)
> +  if (mean(LLb) > threshold) cnt<-cnt+1
> +  }
>> cnt
> [1] 1000
>>
>
>> I would appreciate it if someone could look at the code below and tell
>> me what I am doing wrong.
>>
>> Many thanks,
>>
>> Graham
>>
>>> LL<- c(12.5,17,12,11.5,9.5,15.5,16,14)
>>> N<-1000
>>> n<-length(LL)
>>> threshold<-10
>>> cnt<-0
>>> for(i in 1:N){
>>
>> + LLb <- sample (LL, n, replace=TRUE)
>> + if (mean(LLb)<=threshold) cnt<-cnt+1
>> + }
>>>
>>> cnt
>>
>> [1] 0
>>
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>
> David Winsemius, MD
> Heritage Laboratories
> West Hartford, CT
>
>