Question

If trip A: mean=11, var=3
trip B: mean=5, std dev=1
trip C: mean=24, std dev=5
trip D: mean=18, var=4
The total time taken is Normally distributed.

Part a) What is the mean travel time ?

Part b) What is the standard deviation of the travel time (in minutes, to 2 decimal places)?

Part c) If you need to arrive at 8 am sharp, and you leave from home at 7 am. What is the probability (to 2 decimal places) that you will not be late?

Answer 1

I got it.
the mean is the sum=58,
the standard dev= sqrt(varA+stadB^2+stadC^2+varD)=5.74
the probability(x>z)=0.6368=0.64