Answers and explanations · Turn evidence into a decision-ready story

Lesson 11 answers

11A. Example: “Investigate route and service mix before ranking the hubs. In the 240 recorded synthetic shipments from weeks 1–8, East averaged 79.63 minutes and West 45.96, but East's routes averaged 36.85 km versus 18.67 km and priority shares differed. Late rates were much closer: 25/120 at East and 26/120 at West. These descriptive results do not isolate a causal hub effect. Compare similar service and route groups, review promise definitions and check whether those groups have adequate overlap. Ratings also need a coverage warning because 41 of 240 are missing, with more missingness among late shipments. The current file can guide questions for investigation, but cannot establish that changing hub management will improve outcomes.”

11B. The first is an observation. The second is an interpretation based on selective nonresponse plus the relationship between late status and observed ratings. The third is a recommendation. The missingness pattern suggests a risk; it does not reveal the exact missing ratings or prove the size of any bias.

11C. A causal hub ranking needs comparable design or justified adjustment beyond raw differences; “productivity” requires a defined output/input measure and the trial is simulated; a respondent average cannot automatically represent missing respondents. Repair: “West's recorded mean duration was lower, alongside shorter routes and a different service mix. The simulated checklist mean was about 13.35% lower than control, with uncertain practical benefit and no demonstrated real-world effect. The respondent mean rating was about 4.14 among 199 responses; 41 ratings were missing.”