Chapter 20 is like an extended “What can go wrong?” section from the end of each other chapter in our textbook. In short, even though we might do everything correctly—choose an appropriately random and representative sample of our population, gather our data properly, analyze it accurately, and correctly conduct an appropriate hypothesis test—we might still be wrong. If you missed class (or would like a re-explanation on the rather tricky circumstances that these errors might happen), check out this video. For a slightly more metaphorical take on this subject, watch The Story of Sad Sack and its companion video here.
This weekend, read the first part of chapter 20, pages 516-526 (we will have a reading quiz about the Just Checking questions from this section), then do exercises 4, 5, 7, 13, 17