SOLUTION: 1. A manufacturer of light bulbs produces bulbs that last a mean of 1050 hours with a standard deviation of 100 hours. What is the probability that the mean lifetime of a random sa
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-> SOLUTION: 1. A manufacturer of light bulbs produces bulbs that last a mean of 1050 hours with a standard deviation of 100 hours. What is the probability that the mean lifetime of a random sa
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Question 1174178: 1. A manufacturer of light bulbs produces bulbs that last a mean of 1050 hours with a standard deviation of 100 hours. What is the probability that the mean lifetime of a random sample of 10 of these bulbs is greater than 975 hours?
2. The average public high school has 535 students with a standard deviation of 98.
a. If a public school is selected, what is the probability that the number of students enrolled is less than 550?
b. If a random sample of 25 public high schools is selected, what is the probability that the number of the students enrolled is greater than 600?
You can put this solution on YOUR website! z=(x-mean)/sd/sqrt(n)
> = (975-1050/100/sqrt(10) or -75*sqrt(10)/100 or z>= -2.37
probability is 0.9911
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z < (550-535)/98 or < 15/98=0.15
that probability is 0.5596
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I assume the question means what is the probability that the mean enrollment of these 25 schools is > 600.
This is z > (600-535)/98/sqrt(25) or z > 65/19.6 or > 3.32
that probability is 0.00045 or 0.0005.
