7. A store is expecting n deliveries between the hours of noon and 1 p.m. Suppose the arrival time of each delivery truck is uniformly distributed on this 1-hour interval and that the times are independent of one another.
a) What percentage of the time the latest delivery arrives after 12:50?
b) What percentage of the time the first delivery arrives before 12:10?
Let X denotes arrival time of each delivery.
Since the arrival time of each delivery truck is uniformly distributed on 1 hour interval.
i.e. X ~ U ( 0,60) , one hour interval contain 60 minutes.
The probability distribution of X is
and the cumulative distribution function is
Let X(i) denote the arrival time of ith delivery truck.
n = expected number of deliveries arrive.
a) Let X(n) : arrival time of latest delivery.
X(n) = maximum order statistic.
The probability distribution of maximum order statistic is
Required Percentage = P ( X(n) > 50)
b) Let X(1) : arrival time of first delivery.
X(1) = first order statistic.
The probability distribution of first order statistic is
Required Probability = P ( X(1) < 10)
.
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