A university was interested in examining the overall effectiveness of its online statistics course, along with the effectiveness of particular aspects of the course. First, the university wanted to see whether the online course was better than a standard course. Second, the university wanted to know whether students learned best using Excel, using Minitab, or using no statistical package at all. The university randomly selected a group of 30 students and administered one of the different variants of the course (i. e., traditional or online, coupled with one of the three software options) to each student. The success of each variant was measured by the students' average improvement between a pre-test and a post-test. i. Is this a controlled experiment or observational study?
ii. What are the explanatory variables?
A. The students mean pre-test average score.
B. Whether the course was online or traditional.
C. Whether the course was online or traditional and the statistical software used.
iii. The response variable is:
A. the students' mean post-test score.
B. the difference between the students' mean pre-test and post-test scores.
C. an evaluation of course quality provided by an independent rater.
iv. How many treatment groups are there in this study?
A. 3
B. 4
C. 5
D. 6
E. 7