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Statistics Project

1. A statistics teacher wants to know how her students feel about an introductory statistics

course. She decides to randomly select a class rank (freshmen, sophomores, juniors, and

seniors) and administer a survey to every student in that class rank. Explain why this

plan might be biased. Be sure to name the kind of bias you describe. The researcher is

dividing all population in clusters and are surveying each student. Selection bias occurred.

Freshman, sophomores, juniors, and seniors may not be there to reprsent for statistics

course.

2. Name and describe the kind of bias that might be present if the statistics teacher decides

that instead of randomly selecting students to survey on how they feel about the course

she justâ€¦

a) asks students to volunteer for the survey. Voluntary response bias because students

who enjoy the course would probably be the ones that answered, making the results more

positive.

b) gives the survey one day in class. Convenience bias because only students that are

there are given a chnace to answer the survey.

3. Ivan wants to find out whether people should get abortions, so Ivan sent several surveys

written in English to immigrants who just came to the US and donâ€™t know English. Which

type of bias is this? Explain why.

4. Sharon wants to find out how many people like seafood. Sharon sends out a flier asking

for participants. Which type of bias is this? Explain why.

5. Two different organizations conduct polls in a city whose mayor has been accused of

taking bribes. One poll asks a simple random sample of city residents, â€œDo you think the

mayor should resign because of accusations of his criminal activity?â€ The other asks, â€œDo

you think the mayor should resign?â€ The first poll concluded that the majority of city

residents think the mayor should resign. The second poll drew exactly the opposite

conclusion. Explain why their results might be so different.

6. According to an article on the CNN.com web site titled â€œMajority of U.S. Teens Are Not

Sexually Active, Study Shows,â€ 52% of surveyed teenagers had never had sexual

intercourse. A very large random sample of 16,262 high school students was the source

of this information. If the population of interest consists of all teenagers in the United

States, are there individuals in the population who had no chance of being included in the

sample? What is the name for this type of bias?

7. The article â€œStudy Provides New Data on the Extent of Gambling by College Athletesâ€

reported that â€œ72% of college football and basketball players had bet money at least once

since entering college.â€ This conclusion was based on a study in which â€œcopies of the

survey were mailed to 3000 athletes at 182 Division I institutions, 25% of whom

responded.â€ What types of bias might have influenced the results of this study? Explain.

8. Examine each of the following questions for possible bias. If you think the question is

biased, indicate how and what type of bias. Then propose a better question.

a. Should companies that pollute the environment be compelled to pay the costs of

cleanup?

b. Given that 18-year-olds are old enough to vote and to serve in the military, is it fair

to set the drinking age at 21?

c. Do you think high school students should be required to wear uniforms?

d. Given humanityâ€™s great tradition of exploration, do you favor continued funding for

space flights?

9. Determine whether the study listed is an observational study or an experimental study.

a. A study follows two groups of students, who are randomly selected from a school,

for one year. Students decide which group to join depending on which category

they feel they belong to: I watch more than 10 hours of TV per week OR I watch

fewer than 5 hours of TV per week. Students who watch no television, or who

watch between 5 and 10 hours a week, were excluded from participating in the

study. The study records the average grades and the percent of students who

participate in team sports.

b. A Stat 113 instructor announces a study session to be held the night before a test.

The instructor lists the students who attended the session and compares their

scores to the remaining Stat 113 studentsâ€™ scores.

c. To determine whether a review session will improve his studentsâ€™ test scores, a Stat

113 instructor divides his class into two groups. He then requires one group to

attend a study session and compares the test results of each group.

d. Compare the grades on a final math test of 25 students who use calculators and 25

students who do not use calculators. The students decide which group they are in.

e. Compare voter satisfaction levels between people assigned to use either paper

ballots or touchâ€ screen machines.

f. Determine if people who take vitamin C every day are less likely to get colds.

g. Determine which brands of orange juice people prefer. The people are randomly

chosen at the supermarket and are asked to taste both brands without knowing

which brand they are drinking.

10. Identify the population and the sample:

a. A survey of 1353 American households found that 18% of the households own a

computer.

b. A recent survey of 2625 elementary school children found that 28% of the children

could be classified as obese.

c. The average weight of every sixth person entering the mall within 3 hour period

was 146 lb.

11. Find an example of a â€œbadâ€ graph that illustrates one of the features we said not to use.

Either attach a picture to this worksheet or email a picture to me.

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