Unit 6 · Identifying Sufficient Information

Most Girls Like HP — What's Ms Chen's Mistake?

Lesson 5 of 12

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Ms Chen runs a class survey and learns that most girls want Harry Potter and most boys want Star Wars. She then puts all girls in one room and all boys in the other. Can you spot the logical leap she made? This question teaches one of the most important thinking skills: knowing the difference between "most" and "all."

Chapters

0:00Introduction
0:22The Question
1:23Step 1: Spot Ms Chen's reasoning error
1:50Step 2: What follows from the flaw?
2:10Step 3: Test each option
2:46Correct answer

Question

Ms Chen’s class will be allowed to watch a movie on the last day of term. There are two classrooms available and two televisions, so the class can be split into two, and watch two different movies, if needed. Ms Chen does a survey of the class, asking them what they would like to watch. She notices that most of the girls in the class want to watch Harry Potter, and most of the boys want to watch Star Wars.

Ms Chen says: "There are the same number of boys and girls in the class. So I should put the girls in one classroom and show them Harry Potter, and put the boys in the other classroom to watch Star Wars."”

Which one of the following sentences shows the mistake Ms Chen has made?

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