Section S.1 – Practice Problems

1. A political scientist surveys 28 of the current 106 representatives in a state’s congress. Of them, 14 said they were supporting a new education bill, 12 said there were not supporting the bill, and 2 were undecided.

a. What is the population of this survey?

b. What is the size of the population?

c. What is the size of the sample?

d. Give the sample statistic for the proportion of voters surveyed who said they were supporting the education bill.

2. The city of Raleigh has 9500 registered voters. There are two candidates for city council in an upcoming election: Brown and Felix. The day before the election, a telephone poll of 350 randomly selected registered voters was conducted. 112 said they’d vote for Brown, 207 said they’d vote for Felix, and 31 were undecided.

a. What is the population of this survey?

b. What is the size of the population?

c. What is the size of the sample?

d. Give the sample statistic for the proportion of voters surveyed who said they’d vote for Brown.

3. Studies are often done by pharmaceutical companies to determine the effectiveness of a treatment program. Suppose that a new AIDS antibody drug is currently under study. It is given to patients once the AIDS symptoms have revealed themselves. Of interest is the average (mean) length of time, in months, patients live once they start the treatment. A researcher follows 40 patients with AIDS from the start of treatment until their deaths.

a. What is the population of interest?
b. What is the sample?
c. What is the parameter of interest?
d. What is the statistic?

4. A study was done to determine the age, number of times per week, and the duration (amount of time) of residents using a local park in San Antonio, Texas. The first house in the neighborhood around the park was selected randomly, and then the resident of every eighth house in the neighborhood around the park was interviewed.

a. “Duration (amount of time)” is what type of data, qualitative or quantitative?

b. The colors of the houses around the park are what type of data, qualitative or quantitative?

c. The population is _________________

5. Identify the most relevant source of bias in this situation: A survey asks the following: Should the mall prohibit loud and annoying rock music in clothing stores catering to teenagers?

6. Identify the most relevant source of bias in this situation: To determine opinions on voter support for a downtown renovation project, a surveyor randomly questions people working in downtown businesses.

7. Identify the most relevant source of bias in this situation: A survey asks people to report their actual income and the income they reported on their IRS tax form.

8. Identify the most relevant source of bias in this situation: A survey randomly calls people from the phone book and asks them to answer a long series of questions.

9. Identify the most relevant source of bias in this situation: A survey asks the following: Should the death penalty be permitted if innocent people might die?

10. Identify the most relevant source of bias in this situation: A study seeks to investigate whether a new pain medication is safe to market to the public. They test by randomly selecting 300 men from a set of volunteers.

11. Does this describe an observational study or an experiment? The temperature on randomly selected days throughout the year was measured.

12. Does this describe an observational study or an experiment? A group of students are told to listen to music while taking a test and their results are compared to a group not listening to music.

13. 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. Is this an observational study or an experiment?

14. 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 group. At the end of the semester 12 subjects volunteer and are assigned to the spaced-practice condition. Is this an observational study or an experiment?

15. A team of researchers is testing the effectiveness of a new HPV vaccine. They randomly divide the subjects into two groups. Group 1 receives new HPV vaccine, and Group 2 receives the existing HPV vaccine. The patients in the study do not know which group they are in.

a. Which is the treatment group?

b. Which is the control group (if there is one)?

c. Is this study blind, double-blind, or neither?

d. Is this best described as an experiment, a controlled experiment, or a placebo controlled experiment?

16. For the clinical trials of a weight loss drug containing Garcinia Cambogia the subjects were randomly divided into two groups. The first received an inert (chemically inactive) pill along with an exercise and diet plan, while the second received the test medicine along with the same exercise and diet plan. The patients do not know which group they are in, nor do the fitness and nutrition advisors.

a. Which is the treatment group?

b. Which is the control group (if there is one)?

c. Is this study blind, double-blind, or neither?

d. Is this best described as an experiment, a controlled experiment, or a placebo controlled experiment?