Chapter 6 Practice

Question 1

If x is uniformly distributed over the interval 8 to 12, inclusively (8 x 12), then the probability, P(13 x 15), is ____________ .

	0.250
	0.500
	0.375
	0.000
	1.000

Question 2

If x is uniformly distributed over the interval 8 to 12, inclusively (8 x 12), then P(x 10) is _____________ .

	0.750
	0.000
	0.333
	0.500
	0.900

Question 3

If x, the time (in minutes) to complete an change job at certain auto service station, is uniformly distributed over the interval 20 to 30, inclusively (20 x 30), then the probability that an oil change job is completed in 21.75 to 24.25 minutes, inclusively, i.e., P(21.75 x 24.25) is ____________ .

	0.250
	0.333
	0.375
	0.000
	1.000

Question 4

Let z be a normally distributed random variable with mean 0 and standard deviation 1. What is P(z < 1.3)?

	0.4032
	0.9032
	0.0968
	0.3485
	0. 5485

Question 5

Let z be a normal random variable with mean 0 and standard deviation 1. What is P(z > -1.1)?

	0.36432
	0.8643
	0.1357
	-0.1357
	-0.8643

Question 6

Within a range of z scores from -1 to +1, you can expect to find ______ percent of the values in a normal distribution.

	95
	99
	68
	34
	100

Question 7

Sure Stone Tire Company has established that the useful life of a particular brand of its automobile tires is normally distributed with a mean of 40,000 miles and a standard deviation of 5000 miles. What is the probability that a randomly selected tire of this brand has a life of at least 50,000 miles?

	0.0228
	0.9772
	0.5000
	0.4772
	1.0000

Question 8

The net profit of an investment is normally distributed with a mean of $10,000 and a standard deviation of $5,000. The probability that the investor's net gain will be at least $5,000 is ___________ .

	0.1859
	0.3413
	0.8413
	0.4967
	0.5000

Question 9

The population of lengths of aluminum-coated steel sheets is normally distributed with a mean of 30.5 inches and a standard deviation of 0.2 inches.What is the probability that a sheet selected at random will be less than 31 inches long?

	0.00
	0.9938
	.8289
	.5987

Question 10

An apple juice producer buys all his apples from a conglomerate of apple growers in one northwest state. The amount of juice squeezed from each of these apples is approximately normally distributed with a mean of 2.25 ounces and a standard deviation of 0.15 ounce. What is the probability that a randomly selected apple will contain between 2.00 and 3.00 ounces?

	.0475
	.4525
	.9525
	.9554

Question 11

An apple juice producer buys all his apples from a conglomerate of apple growers in one northwest state. The amount of juice squeezed from each of these apples is approximately normally distributed with a mean of 2.25 ounces and a standard deviation of 0.15 ounce.What is the probability that a randomly selected apple will contain between 2.00 and 2.15 ounces?

	.4525
	.2039
	.2486
	.7011

Question 12

A plant manager knows that the number of boxes of supplies received weekly is normally distributed with a mean of 200 and a standard deviation of 20. What percentage of the time will the number of boxes received weekly be between 180 and 210?

	.6915
	.1915
	.5328
	.1587

Question 13

The starting salaries of individuals with an MBA degree are normally distributed with a mean of $40,000 and a standard deviation of $5,000. What is the probability that a randomly selected individual with an MBA degree will get a starting salary of at least $30,000?

	0.4772
	0.9772
	0.0228
	0.5000

Question 14

The starting salaries of individuals with an MBA degree are normally distributed with a mean of $40,000 and a standard deviation of $5,000. What is the probability that a randomly selected individual with an MBA degree will get a starting salary of at least $47,500?

	0.4332
	0.9332
	0.0668
	0.5000

Question 15

The starting salaries of individuals with an MBA degree are normally distributed with a mean of $40,000 and a standard deviation of $5,000. What percentage of MBA's will have starting salaries of $34,000 to $46,000?

	38.49%
	38.59%
	50%
	76.98%

Question 16

A negative value of Z indicates that

	the number of standard deviations of an observation is to the right of the mean
	the number of standard deviations of an observation is to the left of the mean
	a mistake has been made in computations, since Z cannot be negative
	the data has a negative mean

Question 17

The center of a normal curve is

	always equal to zero
	is the mean of the distribution
	cannot be negative
	is the standard deviation

Question 18

Which of the following is not a characteristic of the normal probability distribution?

	The mean, median, and the mode are equal
	The mean of the distribution can be negative, zero, or positive
	The distribution is symmetrical
	The standard deviation must be 1

Question 19

The weight of football players is normally distributed with a mean of 200 pounds and a standard deviation of 25 pounds. The probability of a player weighing more than 241.25 pounds is

	0.4505
	0.0495
	0.9505
	0.9010

Question 20

The weight of football players is normally distributed with a mean of 200 pounds and a standard deviation of 25 pounds. The probability of a player weighing less than 250 pounds is

	0.4772
	0.9772
	0.0528
	0.5000

Question 21

The weight of football players is normally distributed with a mean of 200 pounds and a standard deviation of 25 pounds. What percent of players weigh between 180 and 215 pounds?

	28.81%
	6.24%
	22.57%
	51.38%

Question 22

The weight of football players is normally distributed with a mean of 200 pounds and a standard deviation of 25 pounds.What is the minimum weight of the middle 95% of the players? (HINT: Apply the Empirical Rule to solve this question)

	196
	150
	249
	190