Let X represent the amount of gasoline (gallons) purchased by a
randomly selected customer at a gas station. Suppose that the mean
value and standard deviation of X are 11.5 and 4.0,
respectively.
a- In a sample of 50 randomly selected customers , what is
the approximate probability that the sample mean amount purchased
is at leat 12 gallons?
b- In a sample of 50 randomly selected customers , what is
the approximate probability that the total amount of gasoline
purchased is at most 600 gallons.
c- What is the approximate value of the 95th
percentile for the total amount purchased by 50 randomly selected
customers.