In: Statistics and Probability
2. Let X1, X2, . . . , Xn be independent, uniformly distributed random variables on the interval [0, θ]. (a) Find the pdf of X(j) , the j th order statistic. (b) Use the result from (a) to find E(X(j)). (c) Use the result from (b) to find E(X(j)−X(j−1)), the mean difference between two successive order statistics. (d) Suppose that n = 10, and X1, . . . , X10 represents the waiting times that the n = 10 people must wait at a bus stop for their bus to arrive. Interpret the result of (c) in the context of this scenario.
A bit theory
Suppose that
denotes a random sample of size m from a continuous pdf f(y) and
cdf F(y), where f(y)>0 for , a<y<b. Then the pdf of i th
order statistic,
be,
Solution
Now here be
independent, uniformly distributed random variables on the interval
with
pdf,
And the cdf as,
(a) So the pdf of j th order statistic be,
(b) Now we have,
(c) So here we have,
(d) So here we suppose that n=10, and
represent the waiting times that the n=10 people must wait at a bus
stop for their bus to arrive. Then
represents j th order waiting time where that person arrived at the
bus stop after n-j people. So here we note that the waiting time
difference of j th and j-1 th person doesnot depend on the value of
j hence it is independent if the ordering of people according to
first come first one to board in the bus basis.
Hence the answer...............
Thank you...........