Question 169754: Can you please show me how to do these two questions.
1. The time a group of high school students arrive home from school each day was found to be normally distributed. The mean time was 3:15 PM and the times had a standard deviation of 15 minutes. What is the probability that a student chosen at random arrives home from school before 2:30 PM?
2. During a clothing sale, 1/4 of the store merchandise is reduced in price. Find the probability that 3 of 5 randomly-selected shirts have reduced prices.
I have to show all my work. Will you please help me.
Thank you
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! 1. The time a group of high school students arrive home from school each day was found to be normally distributed. The mean time was 3:15 PM and the times had a standard deviation of 15 minutes. What is the probability that a student chosen at random arrives home from school before 2:30 PM?
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Find the z-score of 2:30 which is 45 minutes before 3:15.
z(2:30) = (2:30 - 3:15)/15 = -45/15 = -3
P(x < 2:30) = P(z<-3) = 0.00135
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2. During a clothing sale, 1/4 of the store merchandise is reduced in price. Find the probability that 3 of 5 randomly-selected shirts have reduced prices.
I have to show all my work. Will you please help me.
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This is a binomial problem.
n = 5, p = 1/4, x = 3
P(x=3) = 5C3(1/4)^3*(3/4)^2 = 10*(9/4^5) = 0.08789..
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Cheers,
Stan H.
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