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Ch. 1 - Introduction to Statistics
Larson - Elementary Statistics: Picturing the World 8th Edition
Larson8th EditionElementary Statistics: Picturing the WorldISBN: 9780137493470Not the one you use?Change textbook
All textbooksLarson 8th EditionCh. 1 - Introduction to StatisticsProblem 1.r.21
Chapter 1, Problem 1.r.21

200 students volunteer for an experiment to test the effects of sleep deprivation on memory recall. The students will be placed in one of five different treatment groups, including the control group.
Explain how you could design an experiment so that it uses a randomized block design.

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1
Identify the blocking variable: In this case, determine a characteristic that might influence the results of the experiment, such as the students' baseline memory recall ability or their typical sleep patterns. This will be the basis for creating blocks.
Divide the students into blocks: Group the 200 students into blocks based on the chosen characteristic (e.g., high memory recall ability, medium memory recall ability, and low memory recall ability). Ensure that each block is as homogeneous as possible with respect to the blocking variable.
Randomly assign students within each block: Within each block, randomly assign students to one of the five treatment groups, including the control group. This ensures that the randomization accounts for the blocking variable.
Apply the treatments: Administer the specific treatment (e.g., varying levels of sleep deprivation) to each group within each block. The control group will not receive any sleep deprivation treatment.
Measure and compare outcomes: After the treatments, measure the memory recall ability of all students. Analyze the results within each block and across all blocks to determine the effects of sleep deprivation while accounting for the blocking variable.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Randomized Block Design

A randomized block design is an experimental design that involves dividing subjects into blocks based on a specific characteristic, such as age or baseline memory performance. Within each block, participants are randomly assigned to different treatment groups. This method helps control for variability within the blocks, allowing for a clearer assessment of the treatment effects on the outcome variable.
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Control Group

A control group is a baseline group in an experiment that does not receive the treatment or intervention being tested. Instead, it is used for comparison against the treatment groups. This helps researchers determine the effect of the treatment by isolating the impact of the independent variable from other factors that could influence the outcome.
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Random Assignment

Random assignment is the process of assigning participants to different treatment groups in a way that each participant has an equal chance of being placed in any group. This technique minimizes selection bias and helps ensure that the groups are comparable at the start of the experiment, which is crucial for making valid inferences about the treatment effects.
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Related Practice
Textbook Question

You want to know the favorite spring break destination among 15,000 students at a university. Determine whether you would take a census or use a sampling. If you would use a sampling, determine which sampling technique you would use. Explain your reasoning.

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Textbook Question

Identify the sampling technique used, and discuss potential sources of bias (if any). Explain.

A student asks 18 friends to participate in a psychology experiment.

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Textbook Question

200 students volunteer for an experiment to test the effects of sleep deprivation on memory recall. The students will be placed in one of five different treatment groups, including the control group.

Explain how you could design an experiment so that it uses a completely randomized design.

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Textbook Question

"Researchers in Japan tested the effect of cannabidiol (CBD) in treating late teenagers with social anxiety disorder (SAD). Thirty-seven 18- to 19-year-old teenagers with SAD took part in the study. The patients were assigned at random to receive a daily dose of either CBD or a placebo for 4 weeks. Symptoms were measured using The Fear of Negative Evaluation Questionnaire and the Liebowitz Social Anxiety Scale at the beginning and end of the treatment. (Source: Frontiers in Psychology)

How could blocking be used in designing this experiment?"

Textbook Question

A company wants to test the effectiveness of a new acne cream. The company recruits 500 girls ages 13 to 17 who have acne. The subjects are randomly assigned into two groups. One group is given the acne cream and the other is given a placebo that looks exactly like the acne cream. Both groups apply the cream daily for two months. Facial photos are taken at the beginning and end of the treatment to compare results.

c. How could this experiment be designed to be double-blind?

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Textbook Question

Determine whether the study is an observational study or an experiment. Explain.

Researchers conduct a study to determine whether a medication based on fish oil known as omega-3 carboxylic acids is effective in reducing the risk of cardiac events in people already at risk. In the study, 13,078 patients are randomly chosen to receive either omega-3 carboxylic acids or a placebo of corn oil daily. Researchers compare the number of cardiac events of the two groups over similar follow-up periods of time. (Source: American Heart Association)

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