Question

A teacher is experimenting with a new computer-based instruction and conducts a study to test its effectiveness. In which situation could the teacher use the two-sample t-test for comparing two population means?

A) The teacher gives each student in the class a pretest. Then she teaches a lesson using a computer program. Afterwards, she gives each student a post-test.
B) The teacher wants to compare test scores for each student to see whether the data will show an improvement.
C) The teacher randomly divides the class into two groups. One of the groups receives computer-based instruction and the other group receives traditional instruction without computers. After instruction, each student takes a test and the teacher wants to compare the test scores of the two groups.
D) The teacher uses a combination of traditional methods and computer-based instruction. She asks students which they liked better. She wants to determine if the majority prefer the computer-based instruction.

Answer 1

C) The teacher randomly divides the class into two groups. One of the groups receives computer-based instruction and the other group receives traditional instruction without computers. After instruction, each student takes a test and the teacher wants to compare the test scores of the two groups.

Explanation:

Two sample t-test is used when two independent groups exists, and are comparable.

In choices A, B and D the sample of students whose scores will be compared are not independent (do not come from different populations). Therefore two sample t-test cannot be applied here.

In choice C, samples are randomly divided and one group get new computer based instruction and other group get usual instruction. These groups can be seen different populations, since they treated with different methods.