Q1) Major department store has found out that its customers charge the average of $500 per month, with standard deviation of $80. Suppose the amounts of charges are normally distributed.

a) What percentage of customers charges more than $380 per month?

b) What percentage of customers charges less than $340 per month?

c) What percentage of customers' charges between $644 and $700 per month?

Q2) In experiment meant to examine effect of Vitamin A supplements on serum retinol levels in low birth weight (LBW) babies, 65 LBW infants were administered 25,000 IU of Vitamin A.  Sample mean serum retinol level of infants was 45.77, with sample standard deviation s = 17.07.  At α = 0.01, test the claim that vitamin A increased serum retinol level above 12.88micrograms/dl, mean level of serum retinol for all LBW babies.

i) Write the hypothesis statement.

ii) What distribution are you using?

iii) What is the critical value?

iv) What do you conclude?

v) Interpret the p-value.