Data from the Bureau of Labor Statistics\' Consumer Expenditure Survey (CE) show
ID: 3242104 • Letter: D
Question
Data from the Bureau of Labor Statistics' Consumer Expenditure Survey (CE) show that annual expenditures for cellular phone services per consumer unit increased from exist210 in 2001 to exist608 in 2007. Let the standard deviation of annual cellular expenditure be exist48 in 2001 and exist132 in 2007. Use Table 1. What is the probability that the average annual expenditure of 100 cellular customers in 2001 exceeded exist200? (Round "z" value to 2 decimal places, and final answer to 4 decimal places.) Probability _______ What is the probability that the average annual expenditure of 100 cellular customers in 2007 exceeded exist600? (Round "z" value to 2 decimal places, and final answer to 4 decimal places.) Probability _______Explanation / Answer
a) For 2001, mean = 210, s = 48, n = 100
Z score formula is, z = (x - mean)/(s/sqrt(n))
P(X > 200) = 1 - P(X < 200) = 1 - P(Z < (200-210)/(48/sqrt(100))) = 1 - P(Z < -2.08) = 1 - 0.0188(from z table)
= 0.9812
b) For 2007, mean = 608, s = 132, n = 100
P(X > 600) = 1 - P(X < 600) = 1 - P(Z < (600-608)/(132/sqrt(100))) = 1 - P(Z < -0.61) = 1 - 0.2709(from z table)
= 0.7291
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