## CHECK THE BASICS

For Exercise 13.1, see page 302; for Exercise 13.2, see page 304; for Exercise 13.3, see page 306.

### Question 13.4

13.4 Density curves. One characteristic of a density curve is that there is a specific total area under the curve. What is this area equal to?

1. (a) Exactly 1.

2. (b) Approximately 1.

3. (c) It depends on what is being measured.

4. (d) It depends on whether the distribution is Normal.

### Question 13.5

13.5 The mean and median. Which of the following is an incorrect statement?

1. (a) If a density curve is skewed to the right, the mean will be larger than the median.

2. (b) In a symmetric density curve, the mean is equal to the median.

3. (c) The median is the balance point in a density curve.

4. (d) The mean of a skewed distribution is pulled toward the long tail.

### Question 13.6

13.6 Pulse rates. Suppose that resting pulse rates for healthy adults are found to follow a Normal distribution, with a mean of 69 beats per minute and a standard deviation of 9.5 beats per minutes. If Bonnie has a pulse rate of 78.5 beats per minute, this means that

1. (a) approximately 32% of adults have pulse rates higher than Bonnie’s.

2. (b) approximately 16% of adults have pulse rates higher than Bonnie’s.

3. (c) Bonnie’s pulse rate is two standard deviations above the mean.

4. (d) Bonnie’s pulse rate, when converted to a standard score, would be 1.5.

309

### Question 13.7

13.7 More on pulse rates. Let’s again assume that the resting pulse rates for healthy adults follow a Normal distribution with a mean of 69 beats per minute and a standard deviation of 9.5 beats per minute. When converted to a standard score, Adam’s pulse rate becomes −0.5. How should this standard score be interpreted?

1. (a) Adam should see a doctor because his pulse rate is unusually low.

2. (b) Adam’s pulse rate is above the mean.

3. (c) Exactly 5% of healthy adults have pulse rates less than Adam’s pulse rate.

4. (d) Adam’s pulse rate is about one-half of a standard deviation below the mean.

### Question 13.8

13.8 Reading test scores. A standardized reading test is given to fifth-grade students. Scores on this test are Normally distributed, with a mean of 32 points and a standard deviation of 8 points. When Corey gets his test results, he is told that his score is at the 95th percentile. What does this mean?

1. (a) Corey’s score is higher than 95% of the students who took this test.

2. (b) Corey’s score is 48 points.

3. (c) Corey’s score is exactly two standard deviations above the mean.

4. (d) All of the above.