AP Stats Unit 3

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

I. Control of all lurking variables in the experiment.

II. Randomization of subjects to treatment groups.

III. A large number of subjects to control for small-sample variability

• 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 how much sunflowers in three different temperature environments - 15°C, 20°C, and 25°C - respirate (oxygen) in mol/L during germination. 300 sunflowers seeds were each given an equal volume of water (150 mL) each week, each separated randomly into three identical greenhouses. The results were collected. Which of the following is TRUE?

• The experiment is flawed because the 150 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 of over six periods to select from. 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 does not give certainty to its results for its given conditions.

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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 randomly collected in 20 cities on the percentage of women in the workforce in 1990 and in 1994. A two-proportion z-test is performed to determine if there is ongoing discrimination. What kind of design was this?

I. A prospective observational study.

II. A cluster sample survey.

III. A retrospective observational study.

• I only

• II only

• III only

• II and III only

• I and II only

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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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To gather information about the validity of a new standardized test for 10^th grade students in a particular state, a random sample of 15 high schools was selected from the state. The new test was administered to every 10^th grade student in the selected high schools. What kind of sample is this?

• Simple Random Sample (SRS)

• Stratified

• Cluster

• Systematic

• Voluntary response

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