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Difficulty: HardSampling and Generalization Flaws

To evaluate overall soil health and nutrient depletion across a 10,000-acre agricultural region, researchers analyzed soil samples collected exclusively from farms that had reported record-low crop yields during the previous harvest season. Finding that 90 percent of the collected samples exhibited severe nitrogen deficiency, the researchers concluded that the soil throughout the entire region is critically depleted of nitrogen. Which of the following best describes a flaw in the researchers' reasoning?

  1. It draws a sweeping conclusion about the entire region from a sample that is disproportionately drawn from farms prone to poor soil quality.Answer
  2. B
    It presumes without evidence that nitrogen deficiency was the primary cause of the low crop yields reported by the sampled farms.
  3. C
    It fails to consider whether nitrogen levels vary depending on the specific types of crops cultivated across the region.
  4. D
    It overlooks the possibility that chemical fertilization could cause long-term environmental side effects in adjacent ecosystems.
  5. E
    It confuses a decrease in the rate of nitrogen absorption with a decrease in total nitrogen quantity.

Answer

The argument is flawed because it draws a broad conclusion about the entire region from a sample that is disproportionately drawn from farms prone to poor soil quality.
The correct answer identifies a classic selection bias flaw. The researchers attempted to draw a conclusion about all soil across a 10,000-acre region, but gathered data exclusively from farms that experienced record-low crop yields. Farms with poor yields are significantly more likely to have depleted soil than average farms, making the sample unrepresentative of the region as a whole.

Step-by-Step Solution

1
Identify the conclusion and premises
Premise: 90 percent of soil samples taken from low-yield farms showed severe nitrogen deficiency. Conclusion: Soil throughout the entire 10,000-acre region is critically depleted of nitrogen.
Understanding the structural leap from premise to conclusion reveals how the argument arrives at its claim.
2
Evaluate the sample selection method
The sample was drawn exclusively from farms that suffered record-low crop yields, rather than from a randomized cross-section of the region.
Sampling only underperforming farms introduces selection bias, making the sample unrepresentative of healthy or average farms in the area.
3
Select the option that identifies this unrepresentative sampling flaw
The option highlighting that the conclusion relies on a sample disproportionately drawn from farms prone to poor soil quality directly identifies the unrepresentative sampling vulnerability.
An unrepresentative sample cannot justify a general conclusion about an entire population or area.

Key Concept

Sampling and Generalization Flaws
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Topics

Sampling and Generalization Flaws

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