Question 309850: 1. Among cofee drinkers, men drink of 3.2 cups per day with a standard deviation of 0.8 cups. Assume the number of coffee drinks per day follows a normal distribution.
a. What proportion drink 2 cups per day or more?
b. what proportion drink no more than 4 cups per day?
c. If the top 5% coffee drinkers are considered heavy coffe drinkers, what is the minimum number of cups by a heavy coffee drinker? (hint find the 95th percentile.)
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! 1. Among cofee drinkers, men drink of 3.2 cups per day with a standard deviation of 0.8 cups. Assume the number of coffee drinks per day follows a normal distribution.
a. What proportion drink 2 cups per day or more?
z(2) = (2-3.2)/0.8 = -1.5
P(x>= 2) = P(z >= -1.5) = 0.9332
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b. what proportion drink no more than 4 cups per day?
z(4) = (4-3.2)/0.8 = 1
P(x >= 4)=P(z > 1) = 0.1587
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c. If the top 5% coffee drinkers are considered heavy coffe drinkers, what is the minimum number of cups by a heavy coffee drinker? (hint find the 95th percentile.
Find the z-value with a 5% right tail
z = invNorm(0.95) = 1.645
Use x = zs+u to find the number of cups.
x = 1.645*0.8+3.2
x = 4.52
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Cheers,
Stan H.
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