# Chapter 4 — Practice-on-your-own hints — Companion > Diagnostic hints for the Practice-on-your-own problems from Chapter 4 of The Defensible Decision. Canonical URL: https://www.thedefensibledecision.com/ch/04/practice/ [← Chapter 4 companion](/ch/04/) · [All chapter resources](/ch/) Short diagnostic hints for the two Practice on your own problems in this chapter. Attempt each problem before opening the hint. Complete answers appear in Appendix G of The Defensible Decision: Practice Workbook. ### Problem 1 — the churn-attribution chart Restated: A support team asks Copilot to «show why churn increased in Q3.» Copilot returns a bubble chart with three variables mapped to x, y, and bubble size. Name the family Copilot picked, the family the question actually calls for, and the one-sentence direction that would steer to the right family. Show a diagnostic hint Diagnostic cue. Begin with the analytical question, then choose the chart family that makes its comparison visible. Complete answers appear in Appendix G of The Defensible Decision: Practice Workbook. ### Problem 2 — the promo-lift chart Restated: A marketing analyst wants to show the Q3 promotion lifted revenue for three product lines but hurt margin on two. Copilot returns a clustered column chart. Name the two candidate families for this argument, pick the primary, and explain in one paragraph why the other family is a secondary chart, not a shared one. Show a diagnostic hint Diagnostic cue. Separate the relationship claim from the comparison decision before choosing a chart family. Complete answers appear in Appendix G of The Defensible Decision: Practice Workbook. ### Related on this site - [Chapter 4 companion page](/ch/04/) — further reading, self-check quiz, and the chart-family selection activity. - [Chart gallery](/gallery/) — browse chart families with worked examples per family. - [All chapter companion pages](/ch/). - [Feedback](/errata/) — share corrections and improvement opportunities across all chapters. ### About the three-tier Practice format Each chapter of the book closes with a three-tier Practice block adapted from Cole Nussbaumer Knaflic's course-adoption pattern in Storytelling with Data: Let's Practice!: Practice with us (one worked problem with full solution in the book), Practice on your own (open problems with complete answers in Appendix G of the Practice Workbook; this page offers short diagnostic hints), and Practice at work (an open-ended prompt to apply the chapter's move to a live artifact). This page hosts the middle tier.