AP Stats Unit 3 Collecting Data Review

In a study examining the effects of video games on cognitive skills, participants were instructed to play a puzzle game for 30 minutes daily over a month. Their cognitive skills were evaluated at the start and end of the study. The researchers concluded that puzzle games enhance cognitive skills. What is a major flaw in this study's design?

• Evaluation of cognitive skills at the start and end of the study

• Playing a puzzle game for 30 minutes daily

• Conclusion about the effect of puzzle games on cognitive skills

• Absence of a control group not playing puzzle games

Answer explanation

The main mistake in the study is the lack of a control group not playing video games. Without a control group, it's impossible to determine if the observed changes in attention span are due to video games or other factors.

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In a study to evaluate the impact of two different exercise programs on weight loss, participants are randomly assigned to either Program X or Program Y for a duration of three months. Weight is recorded before and after the program. What is the response variable in this study?

• Participants' commitment to the program

• The change in weight

• The type of exercise program

• Weight after three months

Answer explanation

The response variable is what is measured to assess the effect of the diets. In this study, the change in cholesterol levels before and after the diets is the key outcome being evaluated.

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A cluster sampling method was used to study voting patterns in a city by selecting specific neighborhoods. What would happen if a simple random sample was used instead?

• The sample might be more representative of the city's entire voting population, reducing potential bias.

• The study would become more biased, as it would likely overrepresent certain neighborhoods.

• The sample would focus on specific types of voters, reducing the study's generalizability.

• Data collection would be quicker and less expensive, but potentially less accurate.

Answer explanation

Using a simple random sample would likely yield a sample that is more representative of the entire city's voting population, thereby reducing potential bias compared to the cluster sampling method.

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Which of the following is true about replication in experiments?

• It means using the same subjects for all treatments to ensure consistency.

• The treatment should be repeated on enough subjects to make real response differences more apparent.

• It refers to conducting the entire experiment multiple times to ensure accuracy.

• Replication is less important than randomization in an experiment.

Answer explanation

The correct choice highlights that replication involves repeating the treatment on a sufficient number of subjects, which helps to reveal true differences in responses, ensuring the reliability of the experiment's results.

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In the context of experiments, what are experimental units?

• The different levels of the explanatory variable

• The outcomes measured in the experiment

Answer explanation

Experimental units refer to the different levels of the explanatory variable in an experiment. They are the specific conditions or groups that are manipulated to observe their effects on the outcomes measured.

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A market research firm is conducting a survey on consumer preferences for coffee flavors. They decide to interview customers at a popular coffee shop chain. Which type of sampling method are they using?

• Simple random sampling

• Cluster sampling

• Convenience sampling

• Stratified sampling

Answer explanation

The market research firm is using convenience sampling by interviewing customers at a specific coffee shop, which is easily accessible, rather than randomly selecting participants from the entire population.

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Which of the following is an example of sampling variability?

• The variation in responses due to poorly worded questions in a survey.

• The difference in average heights is measured in two different random samples of students from the same school.

• The change in average test scores before and after implementing a new teaching method.

• The difference in average income levels was reported in two surveys conducted in different years.

Answer explanation

Sampling variability refers to the differences in statistics that arise from taking different samples. The correct choice illustrates this by showing the variation in average heights from two random samples of the same population.

Which of the following is an example of sampling bias?

• A study where participants are randomly assigned to two groups.

• A survey conducted only on individuals who have access to the internet.

• A lottery system where every person has an equal chance of being selected.

• A survey where every tenth person entering a mall is interviewed.

Answer explanation

The correct choice is a survey conducted only on individuals with internet access, as it excludes those without access, leading to sampling bias. The other options involve random or systematic sampling methods.

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In a study on the effects of sleep on academic performance, subjects were not informed about the specific nature of the research. What would happen if the study was conducted with blinding?

• Subjects would not know which treatment they received, potentially reducing bias from placebo effects.

• The lack of information would make subjects less cooperative, reducing the study's effectiveness.

Answer explanation

Blinding ensures that subjects are unaware of their treatment, which helps minimize bias from placebo effects. This leads to more reliable results regarding the impact of sleep on academic performance.

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Which of the following is an example of a matched pairs design?

• A study where each participant is given both treatments in random order and their responses are compared.

• A study where two treatments are applied to two different locations to compare their effects.

• A survey where pairs of participants are chosen based on similar characteristics but not given any treatment.

• An experiment where participants are randomly divided into two groups to compare two treatments.

Answer explanation

The correct choice describes a matched pairs design where each participant receives both treatments, allowing for direct comparison of their responses. This controls for individual differences, making it a true matched pairs approach.

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