LSAT 143 | Section 4 | Logical Reasoning: Q9

LR Question 9 Explanation

QUESTION TEXT: In a sample containing 1,000 peanuts from lot A…

QUESTION TYPE: Parallel Reasoning

CONCLUSION: There’s more Aspergillus infection in lot B.

REASONING: A random sample of 1000 peanuts from lots B found that 200 were infected, while only 50 peanuts out of a 1000 were infected in lot A.

ANALYSIS: This is a fairly good argument. The only possible weak points are whether the sample is large enough, and whether the sample was random.

To parallel the argument, you should find a case where there are two fairly large samples, and it’s not mentioned whether they were random.

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1. This is a bad argument. It makes a part-to-whole error. The original argument didn’t make that error.
    
   Example of argument: Every individual peanut here has few calories. So you can eat all 1,000 peanuts without eating many calories.
2. This is a bad argument. Likely = most on the LSAT. You can’t combine two most statements like this.
    
   If we take likely to mean 51%, then it’s possible that a plant only has a 26% chance of death if we mistreat it. (51% odds of blight times 51% odds of death if blight.)
    
   In any case, the original argument didn’t say “most”.
3. This answer isn’t a sample size based argument. The effect happened every time the fungicide was applied. Whereas in the original argument not every peanut was infected.
4. CORRECT. This is a fairly good argument, assuming the sample sizes are large enough and that the samples were random. Same as the peanut argument.
5. This argument uses conditional logic:
    
   Livestock ➞ Registered ➞ Free range
    
   The original argument did not use conditional logic.