DBD assignment1

Answer (end of Chapter 1) questions 5, 7, 13, 17, 21, 25, 27, and 31.
5. In an experiment, researchers measure two types of variables: independent and dependent variables.

(a) Which variable is manipulated to create the groups?
Independent variable
(b) Which variable is measured in each group?

Dependent variable
7. Can a nominal variable be numeric? Explain.

Yes. Just as described in the textbook
(Page 100), numbers on a nominal scale identify something or someone; they provide no additional information. Common examples of nominal numbers include ZIP codes, license plate numbers, credit card numbers, country codes, telephone numbers, and Social Security numbers. These numbers simply identify locations, vehicles, or individuals and nothing more. One credit card number, for example, is not greater than another; it is simply different.
What’s more, a nominal variable could be converted to a numeric value by coding.
13. A researcher measured behavior among all individuals in a small population. Are inferential statistics necessary to draw conclusions concerning this population? Explain.

Inferential statistics are procedures used that allow researchers to infer or generalize observations made with samples to the larger population from which they were selected
(Page 87). So if the research had limited access to the population, then the inferential statistics are necessary; if the small population is small enough to allow the research to have full access, then inferential statistics are not necessary.
17. A researcher measures the height and income of participants and finds that taller men tend to earn greater incomes than do shorter men. What type of research method did the researcher use in this example?

Explain.

It’s correlational method. The correlational method involves measuring the relationship between pairs of scores. No variable is manipulated

and the two variables are measured for each participant, and the extent to which those variables are related is measured. In this case, the researcher measures the relationship between the height and income of participants.
21. Researchers are interested in studying whether personality is related to the month in which someone was born.

(a) What scale of measurement is the month of birth?
Nominal scale.

(b) Is it appropriate to code the data? Explain.

It’s not necessary because coding is the procedure of converting a nominal or categorical variable to a numeric value and the month of birth is already numeric.
25. State whether each of the following is an example of a continuous or discrete variable.

(a) Time in seconds to memorize a list of words
Continuous variable

(b) Number of students in a statistics class
Discrete variable

(c) Weight in pounds of newborn infants
Continuous variable

(d) SAT scores among college students.
Discrete variable
27. Gun ownership in the United States. Data from Gallup polls over a 40-year period show how gun ownership in the United States has changed. The results are described in the table below, with the percent of Americans who own guns given in each of five decades:

Year
%
1972
43
1982
42
1992
48
2002
40
2012
43

Source: Reported at http://www.gallup.com/poll/1645/Guns.aspx

(a) Are the percentages reported here an example of descriptive statistics or interferential statistics?
Descriptive statistics

(b) Based on the percentages given in the table, how has gun ownership in the United States changed over the past 40 years?

From 1972 to 1982, the percent of Americans who own guns declined slightly. It grew in the next decade and decreased in the following decade. Finally it grew back to the same level as that of 1972.
31. Height and educational attainment. Szklarska, Koziel, Bielicki, and

Malina (2007) hypothesized that taller young men are more likely to move up the scale of educational attainment compared with shorter individuals from the same social background. They recruited 91,373 nineteen-year-old men to participate in the study. Do these participants most likely represent a sample or population? Explain.

Sample. A population is the set of all individuals, items, or data of interest. This is the group about which scientists will generalize.

A sample is a set of individuals, items, or data selected from a population of interest.
In this case, all young men would be the population and participates more likely represent a sample of the population.