Refer to the following paragraph to answer the questions below.
Jack Short and Sharon Tall want to increase the percentage of high-school freshmen who pass an algebra exam (dependent variable). They conduct experiments on five sets of classes (named A to E) in Chicago-area schools. They randomly assign students and give a pretest in September followed by a posttest in January. The treatment is the teaching method. The experimental groups are taught with special in-class demonstrations and pictorial games-quizzes on computers, but no homework assignments, textbooks, or tests. The control groups are taught in the traditional way with a textbook, homework assignments, formulas on the blackboard, and tests.

-Looking at all five sets, which set of classes appears to be made up of a nonrandom sample of students from the Chicago-area schools?

Question

Refer to the following paragraph to answer the questions below. 
Jack Short and Sharon Tall want to increase the percentage of high-school freshmen who pass an algebra exam (dependent variable). They conduct experiments on five sets of classes (named A to E) in Chicago-area schools. They randomly assign students and give a pretest in September followed by a posttest in January. The treatment is the teaching method. The experimental groups are taught with special in-class demonstrations and pictorial games-quizzes on computers, but no homework assignments, textbooks, or tests. The control groups are taught in the traditional way with a textbook, homework assignments, formulas on the blackboard, and tests. 
 
-Looking at all five sets, which set of classes appears to be made up of a nonrandom sample of students from the Chicago-area schools?

Quizplus · Accepted Answer

The Answer of Refer to the following paragraph to answer the questions below. 
Jack Short and Sharon Tall want to increase the percentage of high-school freshmen who pass an algebra exam (dependent variable). They conduct experiments on five sets of classes (named A to E) in Chicago-area schools. They randomly assign students and give a pretest in September followed by a posttest in January. The treatment is the teaching method. The experimental groups are taught with special in-class demonstrations and pictorial games-quizzes on computers, but no homework assignments, textbooks, or tests. The control groups are taught in the traditional way with a textbook, homework assignments, formulas on the blackboard, and tests. 
 
-Looking at all five sets, which set of classes appears to be made up of a nonrandom sample of students from the Chicago-area schools?

Refer to the Following Paragraph to Answer the Questions Below