SOLUTION: a study was conducted in oder to determine if any link existed between cellular phone usage and the development of brain cancer. Data from this study indicate that normally phone u

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Question 568103: a study was conducted in oder to determine if any link existed between cellular phone usage and the development of brain cancer. Data from this study indicate that normally phone usage for all users is approximately normally distributed with mean 2.4 hours and standard deviation 1.1 hours.
a. what proportion of cell phone users are on their phones between 1 hour an 3 hours per month?
b. just to be safe, suppose you decide to be in the 5th percentile of cell phone users in terms of monthly usage. how much time can you spend on the phone this month?
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
a study was conducted in order to determine if any link existed between cellular phone usage and the development of brain cancer. Data from this study indicate that normally phone usage for all users is approximately normally distributed with mean 2.4 hours and standard deviation 1.1 hours.
a. what proportion of cell phone users are on their phones between 1 hour an 3 hours per month?
z(1) = (1-2.4)/1.1 = -1.2727
z(3) = (3-2.4)/1.1 = 0.5455
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P(1 <= x <= 3) = P(-1.2727<= z <= 0.5455) = 0.6057
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b. just to be safe, suppose you decide to be in the 5th percentile of cell phone users in terms of monthly usage. how much time can you spend on the phone this month?
Ans:invNorm(0.05) = -1.645
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x = zs + u
x = -1.645*1.1 + 2.4 = 0.5905 hours = 35.43 minutes
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Cheers,
Stan H.
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