A teacher is supposed to be randomly assigning her students to experimental and control groups, for participation in a learning project mandated by the school district
She has a master list of the alphabetized students, numbered 1 through 30. Which of the following is the most logical way to randomly assign the students to groups?
a. Put numbers 1 to 30 in a hat, draw them out one by one, and put them into alternating groups.
b. Place the first 15 subjects in one group and the last 15 in the other group.
c. Ignore numbers and let the students choose their groups.
d. Put numbers 1 to 30 in a hat, draw one, placing it in the experimental group. Then find a student with similar gender, attributes, and abilities, and put that one into the control group. Then go back to the hat for the next experimental subject.
ANS: A
Random assignment is similar to random selection in that elements are selected at random from the sampling frame. To achieve simple random sampling, elements are selected at random from the sampling frame. This goal can be accomplished in a variety of ways, limited only by the imagination of the researcher. If the sampling frame is small, the researcher can write names on slips of paper, place the names in a container, mix well, and then draw out one at a time until the desired sample size has been reached. Another technique is to assign a number to each name in the sampling frame. The traditional "hat draw" is a random method for selection and for assigning. Placing the students into groups by the alphabet is arbitrary, not random. Allowing students to choose their groups turns the study into a quasi-experimental one. Randomly drawing only the experimental subjects one by one and then finding ones with similar attributes to go into the control group is a kind of matching, not random assignment.
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