alleryEditorial: Over the past five years, city buses that installed interior security cameras recorded 40% fewer passenger altercations than buses without cameras. Therefore, installing security cameras on all remaining city buses will significantly improve transit safety across the municipal fleet. Which of the following, if true, most seriously weakens the editorial's argument?
ABuses with cameras were specifically deployed on routes known historically for low passenger crime.
BSecurity cameras cost approximately $1,200 per vehicle to install and maintain.
CPassengers on camera-equipped buses reported feeling safer during evening commutes.
DTransit security officers review recorded camera footage only after an incident is reported.
ECity rail cars that installed cameras experienced a 30% reduction in passenger disputes.
Answer & Solution
Correct answer: A. Buses with cameras were specifically deployed on routes known historically for low passenger crime.
If the camera-equipped buses were assigned to routes that were ALREADY historically low-crime, then the cameras did not cause the 40% reduction; the route selection caused it. This selection bias fatally weakens the causal conclusion.
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