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Difficulty: MediumFlaw in the Reasoning

Agricultural Scientist: In order for a commercial apple orchard to produce export-grade fruit, the soil must maintain an optimal phosphorus-to-nitrogen ratio throughout the spring flowering period. Soil testing across Highland Valley Orchards confirmed that phosphorus and nitrogen levels remained strictly within this optimal ratio throughout the entire spring. Therefore, Highland Valley Orchards will undoubtedly produce fruit of export grade this season.

Which one of the following most accurately describes a flaw in the agricultural scientist's reasoning?

  1. A
    draws a sweeping generalization about all commercial apple orchards based on a sample of orchards that may not be representative
  2. treats a condition that is required for a particular outcome as though it were sufficient to guarantee that outcomeAnswer
  3. C
    attempts to refute a claim by attacking the reliability of the soil testing procedures rather than addressing the substance of the findings
  4. D
    confuses a premise offered in direct support of the conclusion with an intermediate conclusion derived from earlier evidence
  5. E
    presumes without warrant that an orchard failing to maintain the optimal soil ratio will be entirely unable to yield any harvestable crop

Answer

The argument is flawed because it treats a condition that is necessary for achieving export-grade fruit as though it were sufficient to guarantee that outcome.
The scientist's argument establishes that maintaining the optimal phosphorus-to-nitrogen ratio is a necessary requirement ('in order for... must maintain') for producing export-grade fruit. However, the presence of a necessary requirement does not guarantee the outcome, because other necessary factors (e.g., adequate sunlight, pest management, pollination) might not be satisfied. By concluding that the orchard will definitely produce export-grade fruit simply because this one requirement was met, the scientist treats a necessary condition as if it were sufficient.

Step-by-Step Solution

1
Identify the premises and conclusion in the stimulus argument
Premise 1: Producing export-grade fruit requires an optimal phosphorus-to-nitrogen ratio. Premise 2: Highland Valley Orchards maintained this optimal ratio. Conclusion: Highland Valley Orchards will produce export-grade fruit.
Deconstructing the core structural components allows for precise evaluation of the logical link between premises and conclusion.
2
Analyze the conditional relationship established in the first premise
The phrase 'in order for X, Y must occur' establishes Y (optimal soil ratio) as a necessary condition for X (producing export-grade fruit). It does not guarantee X on its own, as other factors (such as pest control, temperature, pollination, and rainfall) may also be required.
Differentiating between necessary and sufficient conditions is essential to pinpointing conditional reasoning vulnerabilities.
3
Identify the logical leap made by the author to reach the conclusion
The author affirms that the necessary condition is met and concludes that the outcome is guaranteed, committing a classic conditional error by confusing necessity with sufficiency.
Matching the identified error to the correct descriptive choice completes the flaw analysis.

Key Concept

Flaw in the Reasoning: Confusing Necessary and Sufficient Conditions
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Topics

Flaw in the Reasoning

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