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Difficulty: MediumCorrelation vs. Causation

Transportation Official: Over the past five years, our city has selectively installed dedicated bicycle lanes in various neighborhoods. Data from the city's traffic department shows that neighborhoods where these bicycle lanes were installed have experienced a significant decrease in average automobile commuting times, whereas neighborhoods without new bicycle lanes have seen their commuting times remain completely stable. Therefore, it is clear that the installation of bicycle lanes is what caused the relief in traffic congestion for drivers in those areas.

Which one of the following most accurately describes a flaw in the transportation official's reasoning?

  1. A
    takes for granted that what is true of the neighborhoods that received new bicycle lanes must also be true of the city's transportation network as a whole.
  2. B
    treats a condition that is sufficient to reduce traffic congestion as if it were a necessary condition for reducing traffic congestion.
  3. fails to consider that an unstated third factor may be independently responsible for both the installation of the bicycle lanes and the decrease in average commuting times.Answer
  4. D
    fails to distinguish between the percentage decrease in commuting times and the absolute number of minutes saved by drivers.
  5. E
    mistakenly identifies the subsidiary premise about stable commuting times in other neighborhoods as the main conclusion of the argument.

Answer

The correct answer identifies that the official assumes a causal relationship (bicycle lanes caused reduced traffic) based entirely on a correlation, ignoring the possibility of a third variable causing both.
The argument commits a classic correlation-to-causation fallacy. The official observes that the installation of bicycle lanes and the decrease in traffic times happened together in certain neighborhoods. From this mere correlation, the official concludes that the bike lanes caused the reduced traffic. The correct answer points out that the official fails to consider an alternative explanation: a third factor (such as a comprehensive neighborhood road-improvement project that included bike lanes) might have simultaneously caused both the installation of the lanes and the improvement in traffic flow.

Step-by-Step Solution

1
Analyze the argument's structure.
Premise: Neighborhoods with new bike lanes saw decreased traffic times; neighborhoods without them saw stable times. Conclusion: The bike lanes caused the decrease in traffic times.
Understanding the precise relationship between the evidence provided and the conclusion drawn is essential for identifying reasoning flaws.
2
Identify the logical flaw.
The official observes a correlation between two events (installation of bike lanes and decreased commuting times) and immediately concludes that one directly caused the other.
Arguments that jump from temporal or statistical correlation to absolute causation are inherently flawed on the LSAT because they ignore alternate explanations.
3
Evaluate the answer choices.
Look for an option that describes the correlation-causation fallacy, such as ignoring alternate causes, reverse causality, or an underlying third common factor.
Matching the abstract flaw identified in the stimulus to the specific descriptions in the choices leads directly to the correct answer.

Key Concept

Correlation vs. Causation
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Topics

Correlation vs. Causation

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