1. A business wants to estimate true mean annual income of its customers. It randomly samples 200 of its customers. The mean annual income was the $52,500 with standard deviation of $1,800. Find out a 95% confidence interval for true mean annual income of business' customers.

2. In standard normal distribution the mean is always ___

a) None of these

b) 1

c) 2

d) 0

3. The area under standard normal curve is

a) None of these

b) 1

c) 0

d) 2