GCU PSY520 Topic 1 Exercises

Complete the following exercises from "Review Questions" located at the end of each chapter and put them into a Word document to be submitted as directed by the instructor.

Chapter 1, numbers 1.8 and 1.9

Chapter 2, numbers 2.14, 2.17, and 2.18

Chapter 3, numbers 3.13, 3.14, 3.18, and 3.19

Chapter 4, numbers 4.9, 4.14, 4.17, and 4.19

Show all relevant work; use the equation editor in Microsoft Word when necessary

Chapter 1

1.8 Indicate whether each of the following studies is an experiment or an

observational study. If it is an experiment, identify the independent variable

and note any possible confounding variables.

(a) A psychologist uses chimpanzees to test the notion that more crowded

living conditions trigger aggressive behavior. Chimps are placed, according

to an impartial assignment rule, in cages with either one, several, or

many other chimps. Subsequently, during a standard observation period,

each chimp is assigned a score based on its aggressive behavior toward a

chimp like stuffed doll.

(b) An investigator wishes to test whether, when compared with recognized,

professional scientists, recognized, professional artists tend to be born

under different astrological signs.

(c) To determine whether there is a relationship between the sexual codes of

primitive tribes and their behavior toward neighboring tribes, an anthropologist

consults available records, classifying each tribe on the basis of

its sexual codes (permissive or repressive) and its behavior toward neighboring

tribes (friendly or hostile).

(d) In a study of group problem solving, an investigator assigns college students

to groups of two, three, or four students and measures the amount

of time required by each group to solve a complex puzzle.

(e) A school psychologist wishes to determine whether reading comprehension

scores are related to the number of months of formal education, as reported

on school transcripts, for a group of 12-year-old migrant children

1.9 Recent studies, as summarized, for example, in E. Mortensen et al. (2002).

The association between duration of breastfeeding and adult intelligence.

Journal of the American Medical Association , 287 , 2365–2371, suggest

that breast-feeding of infants may increase their subsequent cognitive

((IQ) development. Both experiments and observational studies are cited.

(a ) What determines whether some of these studies are experiments?

(b) Name at least two potential confounding variables controlled by breastfeeding

experiments.

Chapter 2

REVIEW QUESTIONS 53

REVIEW QUESTIONS

2.14 (a) Construct a frequency distribution for the number of difference residences

occupied by graduating seniors during their college career,

namely

1, 4, 2, 3, 3, 1, 6, 7, 4, 3, 3, 9, 2, 4, 2, 2, 3, 2, 3, 4, 4, 2, 3, 3, 5

(b) What is the shape of this distribution

*2.17 Are there any conspicuous differences between the two distributions in

the following table (one reflecting the ages of all residents of a small town

and the other reflecting the ages of all U.S. residents)?

(a) To help make the desired comparison, convert the frequencies ( f ) for the

small town to percentages.

(b) Describe any seemingly conspicuous differences between the two distributions.

TWO AGE DISTRIBUTIONS

SMALL TOWN U.S. POPULATION (2010)

AGE f (%)

65–above 105 13

60–64 53 5

55–59 45 6

50–54 40 7

45–49 44 7

40–44 38 7

35–39 31 7

30–34 27 6

25–29 25 7

20–24 20 7

15–19 20 7

10–14 19 7

5–9 17 7

0–4 16 7

Total 500 100%

NOTE: The top class (65–above) has no upper boundary. Although less

preferred, as discussed previously, this type of open-ended class is

employed as a space-saving device when, as in the Statistical Abstract of

the United States, many different tables must be listed.

Source: 2012 Statistical Abstract of the United States.

(c) Using just one graph, construct frequency polygons for the two relative

frequency distributions.

NOTE: When segmenting the horizontal axis, assign the same width to the open ended

interval (65–above) as to any other class interval. (This tactic

causes some distortion at the upper end of the histogram, since one class

interval is doing the work of several. Nothing is free, including the convenience

of open-ended intervals.)

Answers on Page 501.

2.18 The following table shows distributions of bachelor's degrees earned in

2005–2006 for selected fields of study by all male graduates and by all

female graduates.

(a) How many female psychology majors graduated in 2005–2006?

(b) Since the total numbers of male and female graduates are fairly different—

504,600 and 676,000—it is helpful to convert fi rst to relative frequencies

before making comparisons between male and female graduates. Then,

inspect these relative frequencies and note what appear to be the most

conspicuous differences between male and female graduates.

(c) Would it be meaningful to cumulate the frequencies in either of these

frequency distributions?

(d) Using just one graph, construct bar graphs for all male graduates and for

all female graduates. Hint: Alternate shaded and unshaded bars for males

and females, respectively.

BACHELOR'S DEGREES EARNED IN 2005–2006

BY SELECTED FIELD OF STUDY AND GENDER

(IN THOUSANDS)

MAJOR FIELD OF STUDY MALES FEMALES

Business 159.7 158.4

Social sciences 80.8 80.7

Education 22.4 84.8

Health sciences 12.9 79.1

Psychology 19.9 68.3

Engineering 67.0 14.6

Life sciences 26.7 42.5

Fine arts 32.1 51.2

Communications 28.1 48.8

Computer sciences 37.7 9.8

English 17.3 37.8

Total 504.6 676.0

Source: 2007 Digest of Educational Statistics at http://nces.ed.gov.

Chapter 3

72 DESCRIBING DATA WITH AVERAGES

3.13 Garrison Keillor, host of the radio program A Prairie Home Companion ,

concludes each story about his mythical hometown with "That's the

news from Lake Wobegon, where all the women are strong, all the men

are good-looking, and all the children are above average." In what type

of distribution, if any, would

(a) more than half of the children be above average?

(b) more than half of the children be below average?

(c) about equal numbers of children be above and below average?

(d) all the children be above average?

3.14 The mean serves as the balance point for any distribution because the

sum of all scores, expressed as positive and negative distances from the

mean, always equals zero.

(a) Show that the mean possesses this property for the following set of

scores: 3, 6, 2, 0, 4.

(b) Satisfy yourself that the mean identifies the only point that possesses

this property. More specifically, select some other number, preferably a

whole number (for convenience), and then fi nd the sum of all scores in

Part (a) expressed as positive or negative distances from the newly

selected number. This sum should not equal zero.

3.18 Given that the mean equals 5, what must be the value of the one missing

observation from each of the following sets of observations?

(a) 1, 2, 10

(b) 2, 4, 1, 5, 7, 7

(c) 6, 9, 2, 7, 1, 2

3.19 Indicate whether the following terms or symbols are associated with the

population mean, the sample mean, or both means.

(a) N

(b) varies

(c) S

(d) n

(e) constant

(f) subset

Chapter 4

Key Equations

STANDARD DEVIATION FOR SAMPLE

s

SS

df

= = SS

n ?1

where SS X

X

= ? n ( ) ? 2 ?

2

REVIEW QUESTIONS

*4. 9 For each of the following pairs of distributions, fi rst decide whether their

standard deviations are about the same or different. If their standard deviations

are different, indicate which distribution should have the larger

standard deviation. Hint: The distribution with the more dissimilar set of

scores or individuals should produce the larger standard deviation regardless

of whether , on average, scores or individuals in one distribution differ

from those in the other distribution.

(a) SAT scores for all graduating high school seniors (a 1 ) or all college freshmen

(a 2 )

(b) Ages of patients in a community hospital (b 1 ) or a children's hospital (b 2 )

(c) Motor skill reaction times of professional baseball players (c 1 ) or college

students (c 2 )

(d) GPAs of students at some university as revealed by a random sample (d 1 )

or a census of the entire student body (d 2 )

(e) Anxiety scores (on a scale from 0 to 50) of a random sample of college

students taken from the senior class (e 1 ) or those who plan to attend an

anxiety-reduction clinic (e 2 )

(f) Annual incomes of recent college graduates (f 1 ) or of 20-year alumni (f 2 )

Answers on page 503

4.14 (a) Using the computation formula for the sample sum of squares, verify

that the sample standard deviation, s , equals 23.33 lbs for the distribution

of 53 weights in Table 1.1.

(b) Verify that a majority of all weights fall within one standard deviation of the

mean (169.51) and that a small minority of all weights deviate more than

two standard deviations from the mean.

4. 17 Why can't the value of the standard deviation ever be negative?

4.19 Referring to Review Question 2.18 on page 55, would you describe the

distribution of majors for all male graduates as having maximum, intermediate,

or minimum variability?