The distribution of monthly charges for cell phone plans in the US is approximat
ID: 3117206 • Letter: T
Question
The distribution of monthly charges for cell phone plans in the US is approximately normal with a mean of $62 and a standard deviation of $18 A. What percentage of plans have charges that are less than $83.60?B. What percentage of plans have charges that exceed 83.60 The distribution of monthly charges for cell phone plans in the US is approximately normal with a mean of $62 and a standard deviation of $18 A. What percentage of plans have charges that are less than $83.60?
B. What percentage of plans have charges that exceed 83.60 A. What percentage of plans have charges that are less than $83.60?
B. What percentage of plans have charges that exceed 83.60
Explanation / Answer
A) P(x < 83.60)
= P((x - mean)/SD < (83.6 - 62)/18)
= P(Z < 1.2)
= 0.8849 = 88.49%
B) P(X > 83.60)
= P((x - mean)/SD > (83.6 - 62)/18)
= P(Z > 1.2)
= 1 - P(Z < 1.2)
= 1 - 0.8849
= 0.1151 = 11.51%
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