Question 1

Which of the following best describes the purpose of blocking in an experiment?

Accepted Answer

To ensure that each treatment group is as similar as possible with respect to a variable that could affect the outcome.

Question 2

In the laundry detergent experiment, Sue wants to compare four brands for removing grass stains. If she divides uniforms by fabric type before assigning detergents, what is the blocking variable?

Accepted Answer

Fabric type

Question 3

A group of students tests whether popcorn stored in the freezer pops better than at room temperature. They accidentally use two different brands but ignore this when assigning treatments. Which principle of experimental design did they fail to apply?

Accepted Answer

Blocking

Question 4

Which of the following statements about blocking and stratifying is TRUE?

Accepted Answer

Blocking in experiments and stratifying in sampling both group subjects to reduce unwanted variation.

Question 5

In a matched pairs design, what is the main advantage over a completely randomized design?

Accepted Answer

It removes subject-to-subject differences, reducing variability.

Question 6

Suppose you are testing two types of nail polish on the same person, assigning each color to different fingers on each hand. What experimental design is this?

Accepted Answer

Randomized block design

Question 7

Why is randomization within blocks important in a blocked experiment?

Accepted Answer

It helps remove the influence of confounding variables within each block.

Question 8

A researcher pairs subjects by age and then randomly assigns one from each pair to receive a new medication and the other to receive a placebo. What is the blocking variable?

Accepted Answer

Age

Question 9

Which of the following is NOT a reason to use blocking in an experiment?

Accepted Answer

To study the effects of the blocking variable itself.

Question 10

In a matched pairs experiment comparing reading speed on paper versus a Kindle, what is the blocking variable?

Accepted Answer

Each subject

Question 11

Which formula would you use to calculate the difference in means for a matched pairs experiment?

Accepted Answer

$$\overline{d} = \frac{1}{n} \sum_{i=1}^{n} d_i$$

Question 12

A clinical trial assigns patients to two treatments, but first groups them by hospital before randomization. What is this design called?

Accepted Answer

Blocked randomized design

Question 13

Which of the following best explains why we do not study the effects of blocks in a blocked experiment?

Accepted Answer

Blocks are used to control for variation, not to investigate their effects.

Question 14

In a study, 20 patients are paired by gender and age, and within each pair, one receives a new drug and the other a placebo. What is the main benefit of this design?

Accepted Answer

It controls for gender and age differences between subjects.

Question 15

Which of the following is a key difference between blocking and stratifying?

Accepted Answer

Blocking is used in experiments, while stratifying is used in sampling.

Blocking and Matched Pairs in Experimental Design

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