Unit 8 · Detecting Reasoning Errors

Science Fair Rule — Silent Gap & Contrapositive

Lesson 10 of 10

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About this lesson

Now for a formally harder challenge — logical rule analysis. A rule is stated precisely and two characters each draw a conclusion from it. Your job is to evaluate whether each conclusion actually follows from the rule, or whether each person has made a subtle logical mistake.

Chapters

0:00Introduction
0:21The Question
1:18Strategy
2:15Step 1: Decode the rule — one-way arrow and what it stays silent about
3:20Step 2: Leo's reasoning — The Silent Gap (avoiding the Opposite Trap)
4:34Step 3: Sienna's Contrapositive + pick the answer
5:53Correct answer

Question

Whenever a student achieves a High Distinction in the school's annual Science Fair, the administration never includes their name on the list for the mandatory holiday revision program.

Leo: "I didn't achieve a 'High Distinction' in the Science Fair this year. However, that doesn't mean I am definitely on the list for the mandatory holiday revision program — the rule doesn't actually say what happens to students who don't get that award."

Sienna: "I just saw Sarah's name on the mandatory holiday revision program list! That means she definitely did not achieve a High Distinction in the Science Fair."

Read the school administration rule in the box. Then, decide if Leo or Sienna is using logically sound reasoning.

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