The amount of time it takes to serve each customer in a bank is a random variable with a mean of 3.7 minutes and a standard deviation of 2.1 minutes.When you arrive at the bank there are three customers in front of you.The mean of your wait time is 3 × 3.7 = 11.1 minutes.The standard deviation of your wait time is
≈ 3.64 minutes.What assumptions (if any)underlie the calculation of the mean? of the standard deviation?
A)Mean: that the time for each customer follows a Normal model Standard deviation: that the times for the three customers are independent of one another and that the time for each customer follows a Normal model
B)Mean: that the times for the three customers are independent of one another Standard deviation: that the times for the three customers are independent of one another
C)Mean: no assumptions required Standard deviation: that the times for the three customers are independent of one another
D)Mean: no assumptions required Standard deviation: no assumptions required
E)Mean: no assumptions required Standard deviation: that the times for the three customers are independent of one another and that the time for each customer follows a Normal model

Question

The amount of time it takes to serve each customer in a bank is a random variable with a mean of 3.7 minutes and a standard deviation of 2.1 minutes.When you arrive at the bank there are three customers in front of you.The mean of your wait time is 3 × 3.7 = 11.1 minutes.The standard deviation of your wait time is 
≈ 3.64 minutes.What assumptions (if any)underlie the calculation of the mean? of the standard deviation?
A)Mean: that the time for each customer follows a Normal model Standard deviation: that the times for the three customers are independent of one another and that the time for each customer follows a Normal model 
B)Mean: that the times for the three customers are independent of one another Standard deviation: that the times for the three customers are independent of one another 
C)Mean: no assumptions required Standard deviation: that the times for the three customers are independent of one another 
D)Mean: no assumptions required Standard deviation: no assumptions required 
E)Mean: no assumptions required Standard deviation: that the times for the three customers are independent of one another and that the time for each customer follows a Normal model

Quizplus · Accepted Answer

The Answer of The amount of time it takes to serve each customer in a bank is a random variable with a mean of 3.7 minutes and a standard deviation of 2.1 minutes.When you arrive at the bank there are three customers in front of you.The mean of your wait time is 3 × 3.7 = 11.1 minutes.The standard deviation of your wait time is 
≈ 3.64 minutes.What assumptions (if any)underlie the calculation of the mean? of the standard deviation?
A)Mean: that the time for each customer follows a Normal model Standard deviation: that the times for the three customers are independent of one another and that the time for each customer follows a Normal model 
B)Mean: that the times for the three customers are independent of one another Standard deviation: that the times for the three customers are independent of one another 
C)Mean: no assumptions required Standard deviation: that the times for the three customers are independent of one another 
D)Mean: no assumptions required Standard deviation: no assumptions required 
E)Mean: no assumptions required Standard deviation: that the times for the three customers are independent of one another and that the time for each customer follows a Normal model

The Amount of Time It Takes to Serve Each Customer