Chapter 2 - Review Questions

Question 1

What are the symbols of frequency and total scores?

Answer 1

The frequency of a score is symbolized. The total number of scores in the data is symbolized by N.
.

Question 2

What do these symbols mean? N?

Answer 2

Is the number of scores in a sample.

Question 3

What do these symbols mean? f?

Answer 3

Ss the frequency of a score or scores.

Question 4

What is the difference between a bar graph and a histogram?

Answer 4

In a bar graph adjacent bars do not touch; in a histogram they do.

Question 5

With what kind of data is each used?

Answer 5

Bar graphs are used with nominal or ordinal scores; histograms are used with interval or ratio scores.

Question 6

a) What does it mean when a score is in a tail of a normal distribution? (b) What is the difference
between scores in the left-hand tail and scores in the right-hand tail?

Question 7

What is the difference between a score’s simple frequency and its relative frequency?

Answer 7

Simple frequency is the number of times a score occurs; relative frequency is the proportion of time the score occurs.

Question 8

What is the difference between a score’s cumulative frequency and its percentile?

Answer 8

Cumulative frequency is the number of scores at or below a particular score; percentile is usually defined as the percent of the scores below a particular score.

Question 9

(a) What is the advantage of computing relative frequency instead of simple frequency? (b) What is the advantage of computing percentile instead of cumulative frequency?

Question 10

What is the difference between the polygon for a skewed distribution and the polygon for a normal distribution?

Answer 10

A skewed distribution has one distinct tail; a normal distribution has two.

Question 11

What is the difference between the polygon for a bimodal distribution and the polygon for a normal distribution?

Answer 11

A bimodal distribution has two distinct humps above the two highest-frequency scores; a normal distribution has one hump and one highest-frequency score.

Question 12

What is the difference between the graphs for a negatively skewed distribution and a positively skewed distribution?

Question 13

In reading psychological research, you encounter the following statements. Interpret each one. (a) “The IQ scores were approximately normally distributed.” (b) “A bimodal distribution of physical agility scores was observed.” (c) “The distribution of the patients’ memory scores was severely negatively skewed.”

Question 14

What is the difference between how we use the proportion of the total area under the normal curve to determine relative frequency and how we use it to determine percentile?

Answer 14

For relative frequency, we find the proportion of the total area under the curve at the specified scores. For percentile, we find the proportion of the total area under the curve that is to the left of a particular score.

Question 15

What type of frequency graph is appropriate when counting the number of: Blondes, brunettes, redheads, or “others” attending a college?

Answer 15

Bar Graph

Question 16

What type of frequency graph is appropriate when counting the number of: People having each body weight reported in a statewide survey?

Answer 16

Polygon

Question 17

What type of frequency graph is appropriate when counting the number of: Children in each grade at an elementary school? and

Answer 17

Bar Graph

Question 18

What type of frequency graph is appropriate when counting the number of: Car owners reporting above-average, average, or below-average problems with their car?

Answer 18

Histogram

Question 19

The distribution of scores on a statistics test is positively skewed. What does this indicate about the difficulty of the test?

Question 20

The distribution of salaries at a large corporation is negatively skewed. What would this indicate about the pay at this company?

Answer 20

The most frequent salaries tend to be in the middle to high range, with relatively few extremely low salaries.

Question 21

The distribution of salaries at a large corporation is negatively skewed. If your salary is in the tail of this distribution, what should you conclude about your salary?

Answer 21

Yours is one of the lowest, least common salaries.

Question 22

(a) On a normal distribution of exam scores, Crystal scored at the 10th percentile, so she claims that she outperformed 90% of her class. Why is she correct or incorrect? (b) Ernesto’s score is in a tail of the normal curve, so he claims to have one of the highest scores. Why is he correct or incorrect?

Question 23

Interpret each of the following. You scored at the 35th percentile.

Answer 23

35% of the sample scored below you.

Question 24

Interpret each of the following. Your score has a relative frequency of .40.

Answer 24

Your score occurred 40% of the time.

Question 25

Interpret each of the following. Your score is in the upper tail of the normal curve.

Answer 25

It is one of the highest and least frequent scores.

Question 26

Interpret each of the following. Your score is in the left-hand tail of the normal curve.

Answer 26

It is one of the lowest and least frequent scores.

Question 27

Interpret each of the following. The cumulative frequency of your score is 50.

Answer 27

50 participants had either this score or a score below it.

Question 28

Interpret each of the following. Using the area under the normal curve, your score is at the 60th percentile.

Answer 28

60% of the area under the curve is to the left of (below) your score.

Question 29

Draw a normal curve and identify the approximate location of the following scores. (a) You have the most frequent score. (b) You have a low-frequency score, but it is higher than most. (c) You have one of the lower scores, but it has a relatively high frequency. (d) Your score seldom occurred.

Question 30

The following shows the distribution of final exam scores in a large introductory psychology class. The proportion of the total area under the curve is given for two segments. Order the scores 45, 60, 70, 72, and 85 from most frequent to least frequent.

Answer 30

70, 72, 60, 85, 45.

Question 31

The following shows the distribution of final exam scores in a large introductory psychology class. The proportion of the total area under the curve is given for two segments. What is the percentile of a score of 60?

Answer 31

Because .20 of the area under the curve is to the left of 60, it’s at the 20th percentile.

Question 32

The following shows the distribution of final exam scores in a large introductory psychology class. The proportion of the total area under the curve is given for two segments. What proportion of the sample scored below 70?

Answer 32

With .50 of the area under the curve to the left of 70, .50 of the sample is below 70.

Question 33

The following shows the distribution of final exam scores in a large introductory psychology class. The proportion of the total area under the curve is given for two segments. What proportion scored between 60 and 70?

Answer 33

With .50 of the area under the curve below 70, and .20 of the area under the curve below 60, then .50-.20=.30 of the area under the curve is between 60 and 70.

Question 34

The following shows the distribution of final exam scores in a large introductory psychology class. The proportion of the total area under the curve is given for two segments. What proportion scored above 80?

Answer 34

.20.

Question 35

The following shows the distribution of final exam scores in a large introductory psychology class. The proportion of the total area under the curve is given for two segments. What is the percentile of a score of 80?

Answer 35

With .50 below 70 and .30 between 80 and 70, a total of .50+.30=.80 of the curve is below 80, so it is at the 80th percentile.

Question 36

What type of graph should you create when counting the frequency of: The brands of cell phones owned by students? Why?

Answer 36

Bar graph; for a nominal (categorical) variable.

Question 37

What type of graph should you create when counting the frequency of: The different body weights reported in a statewide survey? Why?

Answer 37

Polygon; for many different ratio scores.

Question 38

What type of graph should you create when counting the frequency of: The people falling into one of eight salary ranges? Why?

Answer 38

Histogram; for only 8 different ratio scores.

Question 39

What type of graph should you create when counting the frequency of: The number of students who were absent from a class either at the beginning, middle, or end of the semester? Why?

Answer 39

Bar graph; for an ordinal variable.

Question 40

An experimenter studies vision in low light by having participants sit in a darkened room for either 5, 15, or 25 minutes and then testing their ability to correctly identify 20 objects. (a) What is the independent variable here? (b) What are the conditions? (c) What is the dependent variable? (d) You would use the scores from which variable to create a frequency distribution?

Question 41

Why do we create a bar graph with a nominal or ordinal X variable?

Answer 41

These variables are assumed to be discrete, and the spaces between bars communicate a discrete variable.

Question 42

Why do we connect data points with straight lines with an interval or ratio X variable?

Answer 42

These variables are assumed to be continuous, and the lines between data points communicate that the variable continues between the plotted X scores.