Experimental Design Math Example 3
Follow the full solution, then compare it with the other examples linked below.
Example 3
easyA teacher tests two teaching methods. She teaches Group A (morning) with Method 1 and Group B (afternoon) with Method 2. Identify the confounding variable and explain how to fix the design.
Solution
- 1 Confounding variable: time of day — morning vs. afternoon may affect student alertness and performance, independent of teaching method
- 2 Fix: randomly assign students to groups (not by natural class periods); or teach both methods in both time slots; or block by time of day
Answer
Confound: time of day. Fix with random assignment of students to methods regardless of class period.
Using intact groups (existing classes) instead of random assignment creates confounding. If morning students are more alert, we can't tell if Method 1 is better or if morning alertness is the cause. Random assignment is the solution.
About Experimental Design
The deliberate planning of a study in which the researcher imposes treatments on subjects and measures responses, using control groups, randomization, replication, and (where possible) blinding to establish cause-and-effect relationships.
Learn more about Experimental Design →More Experimental Design Examples
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