Question

The amount of time a bank teller spends with each customer has a population mean of 3.086 minutes. You select a random sample of 16 customers. The sample standard deviation is 0.40 minutes. There is a 95% chance that the sample mean is below ______ minutes

Answer 1

solution:

Given that,

mean = = 3.086

standard deviation = = 0.40

n = 16

= 3.086

= / n = 0.40/16 =0.1

Using standard normal table,

P(Z < z) = 95%

= P(Z < z) = 0.95  

= P(Z <1.65) = 0.95

z =1.65   

Using z-score formula  

= z * +   

= 1.65 *0.1+3.086

= 3.251 minutes

95% chance that the sample mean is below ___3.251___ minutes