Question 1

Which of the following best describes the study design depicted in the diagram above?

Accepted Answer

A randomized block design.

Question 2

In the diagram, why are the fingers grouped into 'Block A: right hand' and 'Block B: left hand' before random assignment to treatments?

Accepted Answer

To control for potential differences between the right and left hands, reducing variability due to hand dominance.

Question 3

What is the primary purpose of random assignment within each block in the experimental design shown?

Accepted Answer

To equalize the effects of unknown or uncontrollable sources of variation within each block.

Question 4

Suppose the experimenter wanted to add a third treatment (e.g., a glitter polish). How would the experimental design change?

Accepted Answer

Each block would be divided into three groups, each randomly assigned to one of the three treatments.

Question 5

If the experimenter did not block by hand (right vs. left), what potential issue could arise?

Accepted Answer

Variation due to hand dominance could confound the results, making it harder to detect treatment effects.

Question 6

Which principle of experimental design is illustrated by grouping fingers by hand before random assignment?

Accepted Answer

Blocking

Question 7

What is the response variable in the experiment depicted in the diagram?

Accepted Answer

Whether the polish chipped or not.

Question 8

If the experimenter compared the results for red and nude polish without random assignment, what risk would increase?

Accepted Answer

The risk of confounding variables influencing the results.

Question 9

Which of the following best explains why blocking is similar to stratification in surveys?

Accepted Answer

Both methods group similar subjects together and randomize within those groups to reduce unwanted variation.

Question 10

If the experimenter wanted to ensure that neither the subjects nor the evaluators knew which treatment was applied to each finger, which experimental design feature should be added?

Accepted Answer

Double-blinding

Experiments and Observational Studies: Principles and Practice

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