AP Stats: Experimental and Sampling Design

Which of the following is (are) important in designing an experiment?

I. Control of all variables that might have an influence on the response variable

II. Randomization of subjects to treatment groups

III. Use of a large number of subjects to control for small-sample variabitility

• I only.

• II only.

• I and II only.

• II and III only.

• I, II, and III

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A botanist wants to test whether sunflowers in three different temperature environments - cold, medium, and hot - can produce more or fewer glucose. The 300 sunflowers seeds were each given an equal volume of water (500 mL), each separated randomly into three identical greenhouses. The results were collected. Which of the following is TRUE?

• The experiment is flawed because the 500 mL of water was not assigned randomly.

• The experiment is flawed because the sunflower seeds were not blocked.

• The explanatory variables are the glucose levels and the temperature of the environments.

• The situation described is an observational study because the botanist did not randomly select the sunflower seeds.

• The results of the study are conclusive only on the basis of cause and effect.

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John Adams, a history teacher, wanted to determine whether short answer or multiple choice were more effective in testing his 86 students’ recall. The students in his first period were given either the short-answer (S) or the multiple choice (M) treatment, via coin flip, into two equally-sized groups. After that, the students may begin their tests. Both treatments contain 20 similar recall questions. This experiment is NOT ideal because John Adams

• utilized a completely randomized design as opposed to a matched-pairs design.

• did not account for students’ grade on the previous assignment.

• did not control for the time given to each treatment group.

• did not randomly select the students from the population of interest.

• created a study that is not generalizable for his 86 students.

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The U.S. Bureau of Labor Statistics collects sample data from households. In the Consumer Expenditure Survey, approximately 500,000 households have been randomly selected to partake in the survey. 300,000 households responded; only 200,000 returned their results, where 20 strata are separated based on income. What is the sample size of the Consumer Expenditure Survey?

• All households of the United States.

• The 500,000 households randomly selected.

• The 300,000 households that responded to the survey.

• The 200,000 households that returned their results.

• The 10,000 households per strata.

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Data were collected in 20 cities on the percentage of women in the workforce in 1990 and in 1994. Gains or losses in this percentage were the measurement upon which the study's conclusion was to be based. What kind of design was this?

I. A matched-pair design

II. An observational study

III. An experiment using a block design

• I only

• II only

• III only

• I and III only

• I and II only

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You want to do a survey of members of the senior class at your school using a simple random sample. You intend to include 40 students in your sample. Which of the following approaches will generate a simple random sample?

• Write the name of each student in the senior class on a slip of paper and put the papers in a container. Then randomly select 40 slips of paper from the container.

• If there are 20 different students per class, select two classes at random and include those students in your sample.

• From a list of all seniors, select one of the first 10 names at random. Then, select every $n$ th name on the list until you have 40 people.

• Select the first 40 seniors to pass through the cafeteria door at lunch.

• Randomly select 10 students from each of the four senior calculus classes.

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Algebra teacher Euler Leonard asked the first 15 students to enter his first period class the amount of time they spend doing their homework using technology. What is a large problem associated with this survey?

• Nonresponse of students.

• Undercoverage of students.

• Response bias from students.

• Convenience sample is used.

• Voluntary response sample is used.

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Which of the following survey demonstrates response bias?

• A survey in which the principle asked the first 100 students to walk in front of his door questions regarding school work.

• 500 randomly selected students had 300 students refuse to respond to any future phone calls.

• 20 football students were asked their feelings about sports in their schools.

• The principle asked each student in each classroom how much time they spent doing their homework.

• "With the price of apples rising because of it, how important is the quality of apples?" is asked of the general consumer in a grocery store.

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The web portal AOL places opinion poll questions next to many of its news stories. Simply click your response to join the sample. One of the questions in January 2008 was "Do you plan to diet this year?" More than 30,000 people responded, with 68% saying "Yes." You conclude that

• about 68% of Americans planned to diet in 2008

• the poll used a convenience sample, so the results tell us little about the population of all adults.

• the poll uses voluntary response, so the results tell us little about the population of all adults.

• the sample is too small to draw any conclusions.

• The poll undercovers the majority of Americans who may not plan to diet.

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A farmer is conducting an experiment to determine which variety of apple tree, Fuji or Gala, will produce more fruit in his orchard. The orchard is divided into 20 equally sized square plots. He has 10 trees of each variety and randomly assigns each tree to a separate plot in the orchard. What are the experimental unit(s) in the study?

• The trees.

• The plots.

• The apples.

• The farmer.

• The tree variety.

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