Question

The weight of packages that are above 5 ounces requires extra postage and 68% of all packages weigh more than 5 ounces. If we need to send 25 packages, what is the expected number of packages that require extra postage? What is the range for the majority number of packages that will require extra postage?

Answer 1

the probability that random packages weigh more than 5 ounces =

for n=25 packages

, the expected number of packages that require extra postage is : np=25*0.68 =17

the standard deviation =

95% of the data lies within 2 standard deviations of the mean

hence the majority number of packages that will require extra postage is