Introduction to Statistics (Online Edition)/Introduction/Exercises

by David M. Lane, David Scott, Mikki Hebl, Rudy Guerra, Dan Osherson, Heidi Zimmer

Exercises

Prerequisites
• All material presented in Chapter: “Introduction”

1. A teacher wishes to know whether the males in his/her class have more conservative attitudes than the females. A questionnaire is distributed assessing attitudes and the males and the females are compared. Is this an example of descriptive or inferential statistics?

2. A cognitive psychologist is interested in comparing two ways of presenting stimuli on sub- sequent memory. Twelve subjects are presented with each method and a memory test is given. What would be the roles of descriptive and inferential statistics in the analysis of these data?

3. If you are told only that you scored in the 80th percentile, do you know from that description exactly how it was calculated? Explain.

4. A study is conducted to determine whether people learn better with spaced or massed practice. Subjects volunteer from an introductory psychology class. At the beginning of the semester 12 subjects volunteer and are assigned to the massed-practice condition. At the end of the semester 12 subjects volunteer and are assigned to the spaced-practice condition. This experiment involves two kinds of non-random sampling: (1) Subjects are not randomly sampled from some specified population and (2) subjects are not randomly assigned to conditions. Which of the problems relates to the generality of the results? Which of the problems relates to the validity of the results? Which problem is more serious?

5. Give an example of an independent and a dependent variable.

6. Categorize the following variables as being qualitative or quantitative:
Rating of the quality of a movie on a 7-point scale
Age
Country you were born in
Favorite Color
Time to respond to a question

7. Specify the level of measurement used for the items in Question 6.

8. Which of the following are linear transformations?
Converting from meters to kilometers
Squaring each side to find the area Converting from ounces to pounds
Taking the square root of each person's height.
Multiplying all numbers by 2 and then adding 5
Converting temperature from Fahrenheit to Centigrade

9. The formula for finding each student’s test grade (g) from his or her raw score (s) on a test is as follows: g = 16 + 3s

Is this a linear transformation?

If a student got a raw score of 20, what is his test grade?

10. For the numbers 1, 2, 4, 16, compute the following:
ΣX
ΣX2
(ΣX)2

11. Which of the frequency polygons has a large positive skew? Which has a large negative skew?

A. B. C.

12. What is more likely to have a skewed distribution: time to solve an anagram problem (where the letters of a word or phrase are rearranged into another word or phrase like “dear” and “read” or “funeral” and “real fun”) or scores on a vocabulary test?

Questions from Case Studies

Angry Moods (AM) case study

13. (AM) Which variables are the participant variables? (They act as independent variables in this study.)

14. (AM) What are the dependent variables?

15. (AM) Is Anger-Out a quantitative or qualitative variable?

Teacher Ratings (TR) case study

16. (TR) What is the independent variable in this study?

ADHD Treatment (AT) case study

17. (AT) What is the independent variable of this experiment? How many levels does it have?

18. (AT) What is the dependent variable? On what scale (nominal, ordinal, interval, ratio) was it measured?