SOLUTION: Suppose, as is roughly true, the number of hours per week ninth-grade students spend playing video games is distributed normally with a mean of 16.8 hours and a standard deviation
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Question 930921: Suppose, as is roughly true, the number of hours per week ninth-grade students spend playing video games is distributed normally with a mean of 16.8 hours and a standard deviation of 3.6 hours.
what is the probability that a single randomly selected ninth-grader spends more than 21 hours each week playing video games?
what is the probability the average of 6 randomly selected ninth-graders spend more than 21 hours each week playing video games?
You can put this solution on YOUR website! mean of 16.8 hours and a standard deviation of 3.6 hours.
P(a single randomly selected ninth-grader spends more than 21 hours )
P(x > 21) = p(z > 4.2/3.6) = P(z > 1.6667) = normalcdf(1.6667, 100) = .0478
........
P(the average of 6 randomly selected ninth-graders spend more than 21 hours )
P( xbar > 21) = P( z > 4.2/(3.6/sqrt(6)) = P(z > 2.8577)= normalcdf(2.8577, 100)= .0021
