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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
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 just…
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
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 don’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, “Do you think the
mayor should resign because of accusations of his criminal activity?” The other asks, “Do
you think the mayor should resign?” 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 “Majority of U.S. Teens Are Not
Sexually Active, Study Shows,” 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 “Study Provides New Data on the Extent of Gambling by College Athletes”
reported that “72% of college football and basketball players had bet money at least once
since entering college.” This conclusion was based on a study in which “copies of the
survey were mailed to 3000 athletes at 182 Division I institutions, 25% of whom
responded.” 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
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 humanity’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 students’ scores.
c. To determine whether a review session will improve his students’ 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 touch‐ 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
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 “bad” 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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