Zion is trying to be more conscious of his energy consumption. In his apartment complex, the average monthly utility bill is $75 with a standard deviation of $8 Last month, Zion's utility bill was $89 What is the z -score for Zion's last month's utility bill? Use the following formula to calculate z -score: z is equal to the fraction with numerator x minus mu and denominator sigma where x is the data point, μ is the mean, and σ is the standard deviation.
Answer
A
2 point 0 - incorrect
B
negative 1 point 5 - no response given
C
1 point 5 - no response given
D
1 point 7 5 - not selected, this is the correct answer
Explanation
Use the z-score formula: z = (x − μ) / σ. Substituting Zion’s bill, the average bill, and the standard deviation gives z = (89 − 75) / 8 = 14 / 8 = 1.75. So the z-score is 1.75, meaning his bill was 1.75 standard deviations above the average. The correct choice is D, “1 point 7 5.”
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