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Week 11 · Module overview

Week 11 — Numbers in the News

Critical Thinking Free sample edition

Welcome to your Week 11 Start Here page.

Why this matters

A nursing student explaining a screening result to a worried family and a business major reading a competitor's chart in a sales meeting both need to know what a number measures, and out of how many, before trusting it.

In plain language

This week is about the numbers inside everyday claims. A rise from 50 percent to 60 percent can be described as 10 percentage points (the plain difference between two percents) or as a 20 percent increase, and both descriptions are true. A risk can double and still touch only a few people, so you learn to ask for the base (the "out of how many" behind a risk). You also learn why most positive results on a test for a rare condition can be false positives (positive results in people who do not have the condition). Finally, you learn to check a graph's axis before you trust its shape.

  • Already covered: Week 1 found premises and conclusions, Week 9 judged samples, and Week 10 checked causes.
  • This week: percentage points, relative and absolute risk, base rates, and misleading graphs.
  • How they connect: claims about samples and causes are often stated in numbers.
  • Where we're going next: Week 12, Evaluating Sources and Evidence.

Focus

What does a number in a claim actually measure, and how much can it carry?

By the end of this module, you should be able to:

  • [ ] report a change in percentage points and as a percent change
  • [ ] give a change in risk both ways with its base named
  • [ ] count the people behind a positive test in natural frequencies
  • [ ] spot a truncated axis, a stretched scale, and a cherry-picked window

To-do

Plan your week

  1. Read Chapter 11 (about 45 minutes), then the lecture and slides.
  2. Work the lecture tutorial (60–90 minutes) and the practice set (about 20 minutes).
  3. Do the Argument Workshop (about 90 minutes), the discussion, and the assignment.
  4. Take the quiz.

This week's checkpoint: explain why only 9 of the 108 people who test positive in the screening table have the condition.

You've got this

Take it in order, and ask your instructor if a step snags.

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