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