[R] help

[Jeff Newmiller]

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Sent from my phone. Please excuse my brevity.

Eva-Lotta Blom <eva-lotta.blom at bioenv.gu.se> 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 + e�� for animals with s ��� 20 20 + s �� 0.8 + e�� for
>animals with s > 20
>
>where �� 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 e�� 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 + e�� for animals with s ��� 20
>time <- 20+S*0.8 [1] #   20 + s �� 0.8 + e�� 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 . Tj��rn��
>University of Gothenburg
>452 96 Str��mstad
>Sweden
>
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