Experimental Designs

Question 162585 • NC-Math 4 CR

Which statement about the randomization for the block design is correct?

Answer

The instructor should place the 25 student names on slips of paper and place them in a hat. Twelve of the slips should be drawn out and those students should receive the instruction on the new technique.

The instructor should place the names of the 14 juniors on slips of paper and place them in one hat. The 11 seniors’ names should be placed on slips of paper and placed into a separate hat. The instructor should randomly select 7 juniors and 5 seniors to receive instruction on the new technique.

For each student, the instructor should flip a coin. If the coin lands on heads, the student will receive instruction on the new technique. If the coin lands on tails, the student will not receive instruction on the new technique.

The students should line up alphabetically and count off by 2s. Every student who gets a 1 will receive instruction on the new technique. Every student who gets a 2 will not receive instruction on the new technique.

Explanation

In a block design, students are first divided into blocks based on a relevant characteristic—in this case, grade level—and then randomized within each block. Choice B selects 7 of the 14 juniors and 5 of the 11 seniors at random, so both grade levels are represented in the treatment group. Choice A randomizes everyone together and could leave one grade level underrepresented.

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