Worked examples
Two examples
Example 1
Kenji wants to know whether a fan helps wet laundry dry faster. He soaks six towels of the same size in the same amount of water. He hangs three towels in front of a fan and three towels in the same room with no fan. He checks every 15 minutes and writes down how long each towel takes to dry.
- The control group gets no treatment, or the usual treatment. It is there for comparison.
- The three towels with no fan are dried the usual way. They are the control group.
- The experimental group gets the change being tested: the three towels in front of the fan.
- Without the control group, Kenji could time the fan towels, but he would have nothing to compare the times with.
Answer: Control: the three towels with no fan. Experimental: the three towels in front of the fan.
Example 2
A school gives every student a new reading app for a year. At the end of the year, the students’ reading scores are higher than at the start. The principal concludes that the app raised the scores.
- Every student got the app. Who did not get it? No one.
- So there is nothing to compare with. The students were a year older and had a year of school. Their scores might have gone up just as much without the app.
- To know what the app did, the school would need a similar group of students, with the same teachers and the same year of school, but without the app.
Answer: A control group
Where this is taught: Science Practices, part 3: The scientific method and a fair test · Look Again Quiz 2: The Scientific Method
In your Kaplan book: Unit 4, Chapter 1, Lesson 2: Use the Scientific Method · Map of the Terrain, topic 2: The scientific method
The drill
Ten questions
Read what is in the box first, if there is one. Then tap your answer; a few questions ask you to choose words from a drop-down instead, the way the GED test does. Press Check my answers at the bottom.Read what is in the box first, if there is one. Circle your answer; where there are brackets, circle the choice that fits. The answer key, with the reasoning, is on the last page.