Chapter 6: Problem 18
Obtain the area under the standard normal curve a. to the right of \(z=1.43\) b. to the left of \(z=-1.65\) c. to the right of \(z=-.65\) d. to the left of \(z=.89\)
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Chapter 6: Problem 18
Obtain the area under the standard normal curve a. to the right of \(z=1.43\) b. to the left of \(z=-1.65\) c. to the right of \(z=-.65\) d. to the left of \(z=.89\)
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A study has shown that \(20 \%\) of all college textbooks have a price of \(\$ 184.52\) or higher. It is known that the standard deviation of the prices of all college textbooks is \(\$ 36.35 .\) Suppose the prices of all college textbooks have a normal distribution. What is the mean price of all college textbooks?
A machine at Keats Corporation fills 64 -ounce detergent jugs. The machine can be adjusted to pour, on average, any amount of detergent into these jugs. However, the machine does not pour exactly the same amount of detergent into each jug; it varies from jug to jug. It is known that the net amount of detergent poured into each jug has a normal distribution with a standard deviation of \(.35\) ounce. The quality control inspector wants to adjust the machine such that at least \(95 \%\) of the jugs have more than 64 ounces of detergent. What should the mean amount of detergent poured by this machine into these jugs be?
Let \(x\) be a continuous random variable that follows a normal distribution with a mean of 550 and a standard deviation of 75 . a. Find the value of \(x\) so that the area under the normal curve to the left of \(x\) is \(.0250\). b. Find the value of \(x\) so that the area under the normal curve to the right of \(x\) is \(.9345\). c. Find the value of \(x\) so that the area under the normal curve to the right of \(x\) is approximately \(.0275 .\) d. Find the value of \(x\) so that the area under the normal curve to the left of \(x\) is approximately . 9600 . e. Find the value of \(x\) so that the area under the normal curve between \(\mu\) and \(x\) is approximately \(.4700\) and the value of \(x\) is less than \(\mu .\) f. Find the value of \(x\) so that the area under the normal curve between \(\mu\) and \(x\) is approximately \(.4100\) and the value of \(x\) is greater than \(\mu\).
Find the following binomial probabilities using the normal approximation. a. \(n=140, \quad p=.45, \quad P(x=67)\) b. \(n=100, \quad p=.55, \quad P(52 \leq x \leq 60)\) c. \(n=90, \quad p=.42, \quad P(x \geq 40)\) d. \(n=104, \quad p=.75, \quad P(x \leq 72)\)
Fast Auto Service guarantees that the maximum waiting time for its customers is 20 minutes for oil and lube service on their cars. It also guarantees that any customer who has to wait longer than 20 minutes for this service will receive a \(50 \%\) discount on the charges. It is estimated that the mean time taken for oil and lube service at this garage is 15 minutes per car and the standard deviation is \(2.4\) minutes. Suppose the time taken for oil and lube service on a car follows a normal distribution. a. What percentage of customers will receive a \(50 \%\) discount on their charges? b. Is it possible that it may take longer than 25 minutes for oil and lube service? Explain.
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