Worked examples
Two examples
Example 1
- The sample is the group actually asked: 4 customers. The sample size is 4.
- 3 of 4 is 3 ÷ 4 = 0.75, or 75 percent.
- If just one of the 3 had said no, it would be 2 of 4: 50 percent.
- One answer moved the result by 25 percentage points. That is why small samples can mislead: chance plays a big part. If she asked 300 customers, one answer would move the result by about a third of a point.
Answer: 75 percent; one different answer would make it 50 percent.
Example 2
- A sample must be like the larger group the claim is about. The claim is about all her customers.
- Customers who come in at 10 p.m. are exactly the people most likely to want late hours.
- So the sample tells her about late-night customers, not about everyone.
- A better sample: customers at every time of day, morning, afternoon and night.
Answer: It is not like all her customers.
Where this is taught: Science Practices, part 5: Reasoning from data · Look Again Quiz 5: Reasoning from Data
In your Kaplan book: Unit 4, Chapter 1, Lesson 3: Reason with Scientific Information · Map of the Terrain, topic 5: Reasoning from data
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.