A government agency publishes ratings of airlines, ranking highest the airlines that have the smallest proportion of late flights. The agency’s purpose is to establish an objective measure of the personnel in meeting published flight schedules.
What this question is testing
Background
The agency ranks airlines by their proportion of late flights — fewer late flights, higher rank.
Conclusion
The agency reads those rankings as a measure of how efficient each airline's personnel are at keeping schedules.
Evaluate
Here is the slip. The data measures lateness — full stop. The agency wants to use it to measure something more specific: how good the people are at their jobs. That works only if personnel are the main reason for lateness or on-time performance.
Imagine ranking restaurants by how often customers leave hungry, and using that ranking to measure how good the chefs are. If some restaurants get power outages more often than others, the ranking will partly reflect bad luck with electricity, not chef skill. The ranking is no longer a clean measure of cooking ability.
Same problem here. If something outside personnel control — like weather — drives a lot of lateness and hits some airlines harder than others, the rankings are partly measuring weather luck, not personnel efficiency.
Goal
Find an answer that shows lateness reflects forces outside personnel control, unevenly distributed across airlines.
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