1. You Are Calculating the Mean and Standard Deviation of 15 Reaction Times in a Psychology

Chapter 1

1. You are calculating the mean and standard deviation of 15 reaction times in a psychology experiment. Each reaction time is measured in seconds. Your results are and s = - 0.12. You conclude that your arithmetic is wrong because

(a) the value is impossible

(b) s must always be larger than

(d) the s value is impossible

2. An important overall strategy in examining data is

(a) don’t trust graphs- do calculations instead

(b) look first for an overall pattern and then for important deviations from that pattern

(d) always use means and standard deviations rather than other measures such as the five-number summary

3. A sample of 56 college students was asked to report the number of hours devoted to study during a typical week. The stem-and-leaf plot of the results is shown below.

STEM-AND-LEAF OF STUDY HOURS(n=50)

0 3

0 5555667777778999

1 0000000000112222333344444

1 5555668

2 0

2 56

3 00

3 5

4 0

Which of the following best describes these data?

(a) Skewed distribution; mean greater than the median

(b) Skewed distribution; mean less than the median

(d) Symmetric distribution; mean less than median

4. Following is a stemplot of a data set of size 125.

1 8

2 001356778899

3 0112333445666678899

4 000111222333445667788

5 00002223333444455566677777888899999999999

6 0001112223445566778899

7 01256679

8 1

What is the median of this set?

(a) 53

(b) 54

(d) 63

5. A distribution of 6 values has a median of 21. If the highest score increases 3 points, the median

will become:

(a) 24

(b) 21.5

(d) cannot be determined

6. In a frequency distribution of 250 scores, the mean is reported as 78 and the median as 65. One

would expect this distribution to be:

(a) skewed right

(b) skewed left

(d) bimodal

7. If you are told a population has a mean of 25 and a variance of 0, what must you conclude?

(a) Someone has made a mistake.

(b) There is only one element in the population.

(d) All the elements in the population are 25.

8. The following data represent yield of alfalfa in tons per acre:

Summary of Yield

Count 54

Mean 2.95348

Median 3.01465

StdDev 0.415509

Min 2.1788

Max 3.5044

Q1 2.7811

Q3 3.2273

Approximately what percent of the data lie between 2.7811 and 3.2273?

(a) 25%

(b) 50%

(d) 75%

9. You are told that your score on a examination was at the 65th percentile. Your score was

(a) above the third quartile

(b) between the median and the third quartile

(d) below the first quartile

10. A professor records the values of several variables for each student in her class. These include the variables listed below. Which of these variables is categorical?

(a) Score on the final exam (out of 200 points).

(b) Final grade for the course (A, B, C, D, or F).

(c) The total number of points earned in the class (i.e., the total of the points on all exams and quizzes in the course; the

maximum number of points possible is 500).

(d) The number of lectures the student missed.

11. Consumers Union measured the gas mileage in miles per gallon of 38 1978–1979 model automobiles on a special test track. The pie chart provides information about the country of manufacture of the model cars used by Consumers Union. Based on the pie chart, we may conclude that

(a) U.S cars get significantly higher gas mileages than cars from other countries.

(b) Swedish cars get gas mileages that are between those of Japanese and U.S. cars.

(d) More than half of the cars in the study were from the United States.

12. Which of the following bar graphs is equivalent to the pie chart?

(a)

(b)

12. Top of Form

(c)

(d)

13. A sample was taken of the salaries of 20 employees of a large company. The following boxplot shows the salaries (in thousands of dollars) for this year.

Based on the boxplot, which of the following statements is true?

(a) The maximum salary is between $60,000 and $70,000.

(b) The minimum salary is $20,000

(d) The median salary is about $40,000

14. If 30 is added to every number on a list, the only one of the following that is not changed is the

(a) mean

(b) mode

(d) standard deviation

15. The five-number summary for scores on a statistics exam is 11, 35, 61, 70, 79. In all, 380 students took the test. About how many had scores between 35 and 61?

(a)35

(b) 61

(d) 190