1. Nick Petritis, Operations Manager with the Palmerston North Trust Bank, is evaluating the service level provided to walk-in customers. Accordingly, his staff recorded the waiting times for 64 randomly selected walk-in customers and determined that their mean waiting time was 15 minutes. Assume that the population standard deviation is 4 minutes. The 90% confidence interval for the population mean of waiting times is:

2. Weekly household expenditure in a country is normally distributed with a mean $1000 and standard deviation of $200.

a)What is the probability that the average weekly expenditure for this sample will be more than $1100?

b)What is the probability that the weekly expenditure of a randomly selected household will be less than $800?

c)What is the probability that the weekly expenditure of a randomly selected household will be more than $1400?

d) If a random sample of 36 households is selected, what is the probability that the weekly expenditure of a randomly selected household will be between $800 and $1200?