Chapter 6

For a normal distribution, proportions in the right-hand tail are positive, and proportions in the left-hand tail are negative. T or F?

False

For a normal distribution, the z-score boundary that separates the highest 2.5% of the scores from the rest is z = -1.96. T or F?

False

The probability of randomly selecting a red marble from a jar that contains 10 red marbles and 20 blue marbles is 1/30. T or F?

False

A vertical line drawn through a normal distribution at z = -0.50 separates the distribution into two sections. The proportions in the larger section is 0.6915. T or F?

True

A vertical line is drawn through a normal distribution so that 47.5% of the distribution is located between the line and the mean. The line is drawn at z = 1.96 or at z -1.96. T or F?

True

All probabilities can be expressed as decimal values ranging from 0 to 1.00. T or F?

True

For any normal distribution, the proportion in the tail beyond z = 2.00 is p = 0.0228. T or F?

True

The proportion in the tail of a normal distribution can never be more than 0.50. T or F?

True

The tail is on the right side of a normal distribution for any z-score value greater than zero. T or F?

True

John drives to work each morning, and the trip takes an average of u = 38 minutes. The distribution of driving times is approximately normal with a standard deviation of ao = 5 minutes. For a randomly selected morning, what is the probability that John's drive to work will take less than 35 minutes?

a) 0.6554 b) 0.3446 c) 0.7257 d) 0.2743*

A vertical line drawn through a normal distribution at z = 0.50 separates the distribution into two sections, the body and the tail. What proportion of the distribution is in the body?

a) 0.6915* b) 0.3085 c) 0.1915 d) 0.3830

IQ scores form a normal distribution with u = 100 and ao = 15. Individuals with IQs between 90 and 110 are classified as average. What proportion of the population is average?

a) 0.7486 b) 0.5028 c) 0.4972* d) 0.2486

What is the probability of randomly selecting a z-score less than z = 1.25 from a normal distribution?

a) 0.8944* b) 0.1056 c) 0.3944 d) 0.2112

What proportion of a normal distribution is located between the mean and z = 1.40?

a) 0.9192 b) 0.0808 c) 0.4192* d) 0.8384

What proportion of a normal distribution is located between z = -1.50 and z = +1.50?

a) 0.9332 b) 0.0668 c) 0.4332 d) 0.8664*

What proportion of a normal distribution is located in the tail beyond z = 1.50?

a) 0.9332 b) 0.0668* c) 0.4332 d) 0.1336

IQ scores form a normal distribution with u = 100 and ao = 15. Individuals with IQs above 140 are classified in the genius category. What proportion of the population consists of geniuses?

a) 0.9962 b) 0.5038 c) 0.4962 d) 0.0038*

A class consists of 10 males and 30 females. If one student is randomly selected from the class, what is the probability of selecting a male?

a) 10/30 b) 10/40* c) 1/10 d) 1/40

A class consists of 10 males and 30 females. A random sample of n = 3 students is selected. If their first two students are both females, what is the probability that the third student is a male?

a) 10/37 b) 10/38 c) 10/40* d) 8/38

Scores on the SAT form a normal distribution with a mean of u = 500 with ao = 100. If the state college only accepts students who score in the top 60% on the SAT, what is the minimum score needed to be accepted?

a) X = 475* b) X = 525 c) X = 440 d) X = 560

Which of the following accurately describes the proportions in the body of a normal distribution?

a) body proportions on the right side of the z-score are greater than 0.50; on the left side, they are less than 0.50 b) body proportions on the right side of the z-score are less than 0.50; on the left side, they are greater than 0.50 c) body proportions on either side of the z-score are less than 0.50 d) body proportions on either side of the z-score are greater than 0.50*

Which of the following is a requirement for a random sample?

a) every individual has an equal chance of being selected b) the probabilities cannot change during a series of selections c) there must be sampling with replacement d) all of the other 3 choices are correct*

Which of the following accurately describes the proportions in the tails of a normal distribution?

a) proportions in the right-hand tail are greater than 0.50, and proportions in the left-hand tail are less than 0.50 b) proportions in the right-hand tail are less than 0.50, and proportions in the left-hand tail are greater than 0.50 c) proportions in both tails are less than 0.50* d) proportions in both tails are greater than 0.50

Which of the following accurately describes the proportions in the tails of a normal distribution?

a) proportions in the right-hand tail are positive, and proportions in the left-hand tail are negative b) proportions in the right-hand tail are negative, and proportions in the left-hand tail are positive c) proportions in both tails are positive* d) proportions in both tails are negative

What z-score value separates the highest 10% of the scores in a normal distribution from the lowest 90%?

a) z = 1.28* b) z = 0.25 c) z = -1.28 d) z = -0.25