[R] Bootstrap

[marcellina79]

I would like to bootstrap the difference between two mean costs (I have a
different number of observations in the two group costs under
consideration).

So, this is my script:
x <- datos$direct_costsUS

fun <- function(x){m=(mean(x[63:136])-mean(x[1:62]))
}

boot.x<- boot(x, 
               statistic = function(d, ind){fun(d[ind])}, 
               R = 5000, 
               sim = "ordinary") 
boot.ci(boot.x, conf = 0.95,type = c("norm","basic","perc","bca"))
####Problem with bca
plot(boot.x)
 
 
This is the final result:
 
Bootstrap Statistics :
    original    bias    std. error
t1* 15.95379 -15.95875    4.792771
 
 
the bias sounds to me really strange.
Do you think my bootstrap procedure is working well?
Thanks a lot for your time.
Best Regards.
Marcella
 
 
 
 
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