The amount of milk sold each day by a grocery store varies according to the Normal distribution with mean 130 gallons and standard deviation 12 gallons. On a randomly selected day, the probability that the store sells at least 154 gallons is

A. 0.0228.
B. 0.1587.
C. 0.8413.
D. 0.9772.

Question

The amount of milk sold each day by a grocery store varies according to the Normal distribution with mean 130 gallons and standard deviation 12 gallons. On a randomly selected day, the probability that the store sells at least 154 gallons is
	
A.	0.0228.
B.	0.1587.
C.	0.8413.
D.	0.9772.

anonymous · Answer

This is an easy P-value problem. Compute the standardized z-score statistic $Z=\frac{154-130}{12}=2.$ You should be familiar with using $\Phi^{-1}$ or a standard normal distribution table for the area of the tail $Z\ge2$... but this problem can be solved with just knowing the empirical rule for standard normal distributions.

anonymous · Answer

http://upload.wikimedia.org/wikipedia/commons/8/8c/Standard_deviation_diagram.svg

anonymous · Answer

and then you subtract the z score by 1