Cutting and pasting your entire homework problem verbatim into an
rhelp posting and assigning it an uninformative subject line and then
expecting a useful response is very hopeful on your part, but those
hopes are unlikely to be realized. You might spend some time reading
the Posting Guide and counting the number of recommendations and
requests in it that you have apparently been ignorant of to this point
in your academic life.
--
David.
On May 15, 2012, at 8:04 AM, Eva-Lotta Blom wrote:
1. Emma is performing an experiment that requires individual
handling of some animals. The sizes of the animals are lognormally
distributed: The natural logarithms of their sizes has a normal
distribution with mean 3 and standard deviation 0.4. The time (in
minutes) it takes to handle each animal is given by
10 + s · 1.5 + eε for animals with s ≤ 20 20 + s · 0.8 + eε for
animals with s > 20
where ε is a random variable that is normally distributed with
expectation 1 and variance 0.3.
For a randomly picked animal, what is the (approximate) probability
that it can be handled in less than 30 minutes?
We can solve this exercise using simulation, as follows: Simulate a
vector S with the sizes of 10000 animals, by using the rnorm
function and the “exp” function. Then, compute a vector Time of
length 10000 with the times it takes to handle each of these 10000
animals: Remember that to separate between the two cases, you can
use notation like for example “Time[S < 20]”. The random
component eε can be added by combining the “exp” function with
the “rnorm” function. Finally, you can find the proportion of
simulated values below 30. Re-do the computations a couple of times
to get an idea of the variability of the result.
s <- c(10000)
S <- exp(rnorm(s, 3, 0.4)) [1]# vector 10000, mean, sd
Time <- 10+S*1.5 [1] # 10 + s · 1.5 + eε for animals with s ≤ 20
time <- 20+S*0.8 [1] # 20 + s · 0.8 + eε for animals with s > 20
can't get any further and i can't really find a good help page to
solve the code.
can you help me?
Lotta
------------------------------------------------------------------------------------
Eva-Lotta Blom PhD student
Dept. of BioEnv . Tjärnö
University of Gothenburg
452 96 Strömstad
Sweden
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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David Winsemius, MD
West Hartford, CT
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