Question

The cost of unleaded gasoline in the Bay Area once followed a normal distribution with a mean of $4.74 and a standard deviation of $0.16. Sixteen gas stations from the Bay area are randomly chosen. We are interested in the average cost of gasoline for the 15 gas stations. What is the approximate probability that the average price for 15 gas stations is over $4.99? it has to be one of the answers below

• A.

  0.0943

• B.

  .0256

• C.

  0.1587

• D.

  0.000

Answer 1

Solution :

= / n = 0.16 / 15 = 0.04131

P( > 4.99) = 1 - P( < 4.99)

= 1 - P[( - ) / < (4.99 - 4.74) / 0.04131]

= 1 - P(z < 6.05)

= 1 - 1

= 0.000

D)