[R] paired t-test with bootstrap

[Petr Pikal]

Hi

On 13 Jul 2004 at 12:28, luciana wrote:

> Dear Sirs,
> 
> I am a R beginning user: by mean of R I would like to apply the
> bootstrap to my data in order to test cost differences between
> independent or paired samples of people affected by a certain
> disease.
> 
> My problem is that even if I am reading the book by Efron
> (introduction to the bootstrap), looking at the examples in internet
> and available in R, learning a lot of theoretical things on
> bootstrap, I can't apply bootstrap with R to my data because of many
> doubts and difficulties. This is the reason why I have decided to
> ask the expert for help.
> 
> 
> 
> I have a sample of diabetic people, matched (by age and sex) with a
> control sample. The variable I would like to compare is their drug
> and hospital monthly cost. The variable cost has a very far from
> gaussian distribution, but I need any way to compare the mean
> between the two group. So, in the specific case of a paired sample
> t-test, I aim at testing if the difference of cost is close to 0.
> What is the better way to follow for that?
> 
> 
> 
> Another question is that sometimes I have missing data in my dataset
> (for example I have the cost for a patients but not for a control).
> If I introduce NA or a dot, R doesn't estimate the statistic I need
> (for instance the mean). To overcome this problem I have replaced
> the missing data with the mean computed with the remaining part of
> data. Anyway, I think R can actually compute the mean even with the
> presence of missing data. Is it right? What can I do?

your.statistic(your.data, na.rm=T)

e.g.
mean(your.data, na.rm=T)

or look at ?na.action e.g  mean(na.omit(your.data))

Cheers
Petr Pikal


> 
> 
> 
> Thank you very much for your attention and, I hope, your help.
> 
> 
> 
> Best wishes 
> 
> 
> 
> Luciana Scalone
> 
> Center of Pharmacoeconomics
> 
> University of Milan
> 
>  [[alternative HTML version deleted]]
> 
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Petr Pikal
petr.pikal at precheza.cz