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Difficulty: Very hardFlaw in the Reasoning

Epidemiologist: Any localized outbreak of the viral strain H7N2 in this region is preceded by a sharp increase in the population of the invasive mosquito species Aedes albopictus. Furthermore, a sharp increase in this mosquito population inevitably leads to a higher rate of hospitalization for vector-borne illnesses in the affected area. Over the last month, Riverside County has seen a significant spike in hospitalizations for vector-borne illnesses, and entomologists have confirmed a massive surge in the local Aedes albopictus population. We can safely conclude, therefore, that an outbreak of the H7N2 viral strain has occurred in Riverside County.

The epidemiologist's argument is most vulnerable to criticism on the grounds that it...

  1. treats a condition that must be present for a specific phenomenon to occur as a condition whose presence guarantees the occurrence of that phenomenonAnswer
  2. B
    takes for granted that the Aedes albopictus mosquito is the only insect capable of transmitting the H7N2 viral strain in this region
  3. C
    overlooks the possibility that a sharp increase in the mosquito population might not always lead to a higher rate of hospitalizations
  4. D
    treats a condition that is sufficient to produce an increase in hospitalizations as a condition that is necessary to produce that increase
  5. E
    inappropriately relies on the assumption that an outbreak of the H7N2 viral strain will always result in the most severe symptoms associated with vector-borne illnesses

Answer

The correct answer is the option stating that the argument treats a condition that must be present for a specific phenomenon to occur as a condition whose presence guarantees the occurrence of that phenomenon.
The argument contains a classic formal logic flaw known as Mistaken Reversal. The first premise establishes that a viral outbreak is always preceded by a mosquito surge, meaning the surge is a necessary condition for an outbreak to have occurred (Outbreak → Mosquito Surge). However, the author takes the confirmed presence of this necessary condition (the mosquito surge) as definitive proof that the outbreak actually happened. By doing so, the author treats a condition that must be present for a phenomenon to occur as a condition that guarantees its occurrence.

Step-by-Step Solution

1
Identify the premises and the main conclusion of the argument.
Premise 1: Outbreak implies prior Mosquito Surge. Premise 2: Mosquito Surge implies Increased Hospitalizations. Premise 3: Hospitalizations and Mosquito Surge occurred. Conclusion: Outbreak occurred.
Breaking down the argument into its formal logic components is essential for identifying structural vulnerabilities.
2
Analyze the logical relationship between the viral outbreak and the mosquito population surge.
The argument states that an outbreak is 'preceded by' a mosquito surge. This makes the surge a necessary condition for an outbreak to have occurred.
Determining necessary and sufficient conditions reveals the exact direction of the logical relationship.
3
Evaluate how the author draws the conclusion from the observed evidence.
The author observes that the necessary condition (mosquito surge) is present, and incorrectly uses this to conclude that the sufficient condition (viral outbreak) must have also occurred.
This step isolates the fundamental gap between the provided evidence and the drawn conclusion.
4
Formulate an abstract description of this specific reasoning error.
The author commits a conditional reversal, mistakenly treating a necessary precondition as a sufficient guarantee.
Matching the specific error to its abstract structural description is required to select the correct option.

Key Concept

Conditional Reasoning: Mistaken Reversal
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Topics

Flaw in the Reasoning

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