Worked examples
Two examples
Example 1
Ana wants to know whether a new dish soap cuts grease better than her usual one. She washes a greasy pan with the new soap in hot water. Then she washes another greasy pan with her usual soap in cold water. The first pan comes out cleaner, and she concludes that the new soap is better.
- Most flaws are one of four: more than one thing was changed; there was no control group; too few trials or subjects; or the conclusion claims more than the data show.
- Ask: what was different between the two pans? The soap, and also the water: hot for one, cold for the other.
- Hot water cuts grease by itself. The first pan may be cleaner because of the water, with no help from the soap.
- To fix it: use the same water temperature for both, change only the soap, and wash several pans with each soap.
Answer: More than one thing was changed.
Example 2
At one school, students who ate breakfast scored higher, on average, on a morning quiz than students who skipped breakfast. The principal announces: “Eating breakfast makes every student smarter.”
- Say the finding in plain words: at one school, on one quiz, the students who ate breakfast scored higher on average.
- Now compare the principal’s words with that. “Every student” and “smarter” go far beyond one quiz at one school.
- The data also show only that two things went together. They do not show that breakfast caused the higher scores.
Answer: The conclusion claims more than the data show.
Where this is taught: Science Practices, part 3: Spotting the flaw · Look Again Quiz 2: The Scientific Method · Change One Thing, the scientific method app
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.