Q1) A business wishes to evaluate true mean annual income of its customers. It randomly samples 200 of its customers. Mean annual income was= $52,500 with standard deviation of $1,800. Determine a 95% confidence interval for true mean annual income of business' customers.

Q2) In standard normal distribution mean is always ___

a) None of these

b) 1

c) 2

d) 0

Q3) Area under standard normal curve is

a) None of these

b)1

c) 0

d) 2

Q4) What is critical z-value which corresponds to confidence level of 88%

a) Approximately1.75

b) Approximately1.55

c) Approximately1.48

d)Approximately2.11

Q5) Interpret 95% confidence interval of (3.355, 3.445) for population mean.

Q6) In normal distribution with mu = 25 and sigma = 3 what number corresponds to z = -3?

A) 20

B) 16

C) 18

D) None of these