SOLUTION: A supermarket manager wishes to make an estimate of the average time in minutes a customer spends at the checkout counter. It is known from previous studies that the variance is 8.
Algebra ->
Probability-and-statistics
-> SOLUTION: A supermarket manager wishes to make an estimate of the average time in minutes a customer spends at the checkout counter. It is known from previous studies that the variance is 8.
Log On
Question 1193302: A supermarket manager wishes to make an estimate of the average time in minutes a customer spends at the checkout counter. It is known from previous studies that the variance is 8.1. How large a sample is required if she wants a 95% confidence interval for the population mean that extends no further than 1 minutes from the sample mean. Round up your answer to a whole number. Answer by Boreal(15235) (Show Source):
You can put this solution on YOUR website! error=z(0.975)*change in mean/sigma/sqrt(n)
sigma=sqrt(V)=2.85
1=1.96*2.85/sqrt(n)
square both sides
1=3.8416*8.1/n
n=31.12=32, rounding up
