# Multiple Choice

38. A standard normal distribution has the following characteristics:

a) the mean and the variance are both equal to 1

b) the mean and the variance are both equal to 0

c) the mean is equal to the variance

d) the mean is equal to 0 and the variance is equal to 1

e) the mean is equal to the standard deviation

Ans:

Response: See section 6.2, Normal Distribution

Difficulty: Medium

39. If x is a normal random variable with mean 80 and standard deviation 5, the z-score for x = 88 is ________.

a) 1.8

b) -1.8

c) 1.6

d) -1.6

e) 8.0

Ans:

Response: See section 6.2, Normal Distribution

Difficulty: Medium

40. Suppose x is a normal random variable with mean 60 and standard deviation 2.  A z score was calculated for a number, and the z score is 3.4.  What is x?

a) 63.4

b) 56.6

c) 68.6

d) 53.2

e) 66.8

Ans:

Response: See section 6.2, Normal Distribution

Difficulty: Medium

41. Suppose x is a normal random variable with mean 60 and standard deviation 2.  A z score was calculated for a number, and the z score is -1.3.  What is x?

a) 58.7

b) 61.3

c) 62.6

d) 57.4

e) 54.7

Ans:

Response: See section 6.2, Normal Distribution

Difficulty: Medium

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

a) 0.4032

b) 0.9032

c) 0.0968

d) 0.3485

e) 0. 5485

Ans:

Response: See section 6.2, Normal Distribution

Difficulty: Medium

43. Let z be a normal random variable with mean 0 and standard deviation 1. What is P(1.3 < z < 2.3)?

a) 0.4032

b) 0.9032

c) 0.4893

d) 0.0861

e) 0.0086

Ans:

Response: See section 6.2, Normal Distribution

Difficulty: Medium

44. Let z be a normal random variable with mean 0 and standard deviation 1. What is P(z > 2.4)?

a) 0.4918

b) 0.9918

c) 0.0082

d) 0.4793

e) 0.0820

Ans:

Response: See section 6.2, Normal Distribution

Difficulty: Easy

45. Let z be a normal random variable with mean 0 and standard deviation 1. What is P(z < -2.1)?

a) 0.4821

b) -0.4821

c) 0.9821

d) 0.0179

e) -0.0179

Ans:

Response: See section 6.2, Normal Distribution

Difficulty: Medium

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

a) 0.36432

b) 0.8643

c) 0.1357

d) -0.1357

e) -0.8643

Ans:

Response: See section 6.2, Normal Distribution

Difficulty: Medium

47. Let z be a normal random variable with mean 0 and standard deviation 1. What is

P(-2.25 < z < -1.1)?

a) 0.3643

b) 0.8643

c) 0.1235

d) 0.4878

e) 0.5000

Ans:

Response: See section 6.2, Normal Distribution

Difficulty: Medium

48. Let z be a normal random variable with mean 0 and standard deviation 1. The 50th percentile of z is ____________.

a) 0.6700

b) -1.254

c) 0.0000

d) 1.2800

e) 0.5000

Ans:

Response: See section 6.2, Normal Distribution

Difficulty: Easy

49. Let z be a normal random variable with mean 0 and standard deviation 1. The 75th percentile of z is ____________.

a) 0.6700

b) -1.254

c) 0.0000

d) 1.2800

e) 0.5000

Ans:

Response: See section 6.2, Normal Distribution

Difficulty: Medium

50. Let z be a normal random variable with mean 0 and standard deviation 1. The 90th percentile of z is ____________.

a) 1.645

b) -1.254

c) 1.960

d) 1.280

e) 1.650

Ans:

Response: See section 6.2, Normal Distribution

Difficulty: Medium

51.          A z score is the number of __________ that a value is from the mean.

a) variances

b) standard deviations

c) units

d) miles

e) minutes

Ans:

Response: See section 6.2, Normal Distribution

Difficulty: Easy

52.          Within a range of z scores from -1 to +1, you can expect to find _______ per cent of the values in a normal distribution.

a) 95

b) 99

c) 68

d) 34

e) 100

Ans:

Response: See section 6.2, Normal Distribution

Difficulty: Easy

53.          Within a range of z scores from -2 to +2, you can expect to find _______ per cent of the values in a normal distribution.

a) 95

b) 99

c) 68

d) 34

e) 100

Ans:

Response: See section 6.2, Normal Distribution

Difficulty: Easy

54.          The expected (mean) life of a particular type of light bulb is 1,000 hours with a standard deviation of 50 hours.  The life of this bulb is normally distributed.  What is the probability that a randomly selected bulb would last longer than 1150 hours?

a) 0.4987

b) 0.9987

c) 0.0013

d) 0.5013

e) 0.5513

Ans:

Response: See section 6.2, Normal Distribution

Difficulty: Medium

55.          The expected (mean) life of a particular type of light bulb is 1,000 hours with a standard deviation of 50 hours. The life of this bulb is normally distributed. What is the probability that a randomly selected bulb would last fewer than 1100 hours?

a) 0.4772

b) 0.9772

c) 0.0228

d) 0.5228

e) 0.5513

Ans:

Response: See section 6.2, Normal Distribution

Difficulty: Medium

56.          The expected (mean) life of a particular type of light bulb is 1,000 hours with a standard deviation of 50 hours. The life of this bulb is normally distributed.  What is the probability that a randomly selected bulb would last fewer than 940 hours?

a) 0.3849

b) 0.8849

c) 0.1151

d) 0.6151

e) 0.6563

Ans:

Response: See section 6.2, Normal Distribution

Difficulty: Medium

57.          Suppose you are working with a data set that is normally distributed with a mean of 400 and a standard deviation of 20.  Determine the value of x such that 60% of the values are greater than x.

a) 404.5

b) 395.5

c) 405.0

d) 395.0

e) 415.0

Ans:

Response: See section 6.2, Normal Distribution

Difficulty: Hard

58.          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 most 30,000 miles?

a) 0.5000

b) 0.4772

c) 0.0228

d) 0.9772

e) 1.0000

Ans:

Response: See section 6.2, Normal Distribution

Difficulty: Hard

59.          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?

a) 0.0228

b) 0.9772

c) 0.5000

d) 0.4772

e) 1.0000

Ans:

Response: See section 6.2, Normal Distribution

Difficulty: Hard

60.          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 between 30,000 and 50,000 miles?

a) 0.5000

b) 0.4772

c) 0.9544

d) 0.9772

e) 1.0000

Ans:

Response: See section 6.2, Normal Distribution

Difficulty: Hard

61.          The net profit from a certain investment is normally distributed with a mean of \$10,000 and a standard deviation of \$5,000. The probability that the investor will not have a net loss is _____________.

a) 0.4772

b) 0.0228

c) 0.9544

d) 0.9772

e) 1.0000

Ans:

Response: See section 6.2, Normal Distribution

Difficulty: Hard [checkout]