Question

Question 8 of 20 points Attempt of Viewestion in a h man Electricity bills According to a government energy agency, the mean monthly household electricity be in the United States in 2011 was $109.72. Assume the amounts are normally distributed with standard deviation $24.00. Use the TI-84 Muscalculator to answer the following. (a) What proportion of bills are greater than $1317 (b) What proportion of bills are between 587 and $140? (c) What is the probability that a randomly selected household had a monthly bill less than $1257 Round the answers to at least four decimal places. Part 1 of 3 The proportion of bills that are greater than $131 is . Part 2 of 3 The proportion of bills that are between $87 and $140 is . Part 3 of 3 I. The probability that a randomly selected household had a monthly bill less than $125 is

Answer 1

Part 1 of 3: P(X>131)=1- P(X <131) X-4 131-109.72 =1- P(Z <0.89) =1 -0.8133 = 0.1867 The proportion of bills that are greater than $131 is 0.1867.

Part 2 of 3: 7-4 87–109.72 24 P(87< X <140) = P(X 5140) - P(X 387) X-4 140-109.72) lo 24 = P(Z <1.26)-P(Z <-0.95) = 0.8962 -0.1711 =0.7251 The proportion of bills that are between $87 and $140 is 0.7251. Part 3 of 3: I-4 125-109.72 P(X<125) = Polans 24/11) = P(Z <0.64) = 0.7389 The proportion of bills that are less than $125 is 0.7389.