



 
Hi Claudia, I let the random variable X be the time after 8:00 in minutes. Thus 0 ≤ X ≤ 30. Sine the employee is equally likely to arrive at any time X the probability density function f(x) is the uniform distribution so f(x) = 1/30. The first question is asking for the mean of this distribution, that is the average time the employee arrives after 8:00 is The standard deviation is the square root of the variance Var(X) where Can you see how to complete the problem?  


Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences. 