Suppose that we have two normal populations with samples of size 25 are
drawn from each population, what is the probability that the mean of sample 1
is greater than the mean of sample 2? (20%)
Population 1:μ = 40 ,σ = 6 ;
Population 2: μ = 38 ,σ = 8.
Let X be a continuous random variable with density function f (x) = 2x−3 ,
x >1 . Find the mean and variance of X . (20%)
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