Question 1

Which of the following best describes the study design depicted in the diagram, where fingers are grouped by hand before random assignment to treatments?

Accepted Answer

A randomized block design

Question 2

In the diagram, why are the fingers first grouped by hand (right hand vs. left hand) before random assignment to treatments?

Accepted Answer

To control for potential differences between hands, reducing variability due to hand differences

Question 3

Suppose the outcome measured is whether the nail polish chipped. What is the response variable in this experiment?

Accepted Answer

Whether the polish chipped

Question 4

What is the main 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 5

If the experimenter had not blocked by hand and simply assigned treatments randomly to all fingers, what potential issue could arise?

Accepted Answer

Differences between hands 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

Block

Question 7

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

Accepted Answer

Each group within each block would be randomly assigned to one of three treatments

Question 8

What is the main advantage of using a randomized block design as shown in the diagram?

Accepted Answer

It isolates variability due to blocking variables, making treatment effects easier to detect

Question 9

In the context of this experiment, what would be an example of a confounding variable if blocking by hand was not used?

Accepted Answer

The dominant hand of the participant, if it affects chipping

Question 10

If the experimenter wanted to ensure that neither the subjects nor the evaluators knew which treatment was applied to each finger, what type of blinding would this require?

Accepted Answer

Double-blind

Experiments and Observational Studies: Principles and Practice

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