Logical Reasoning

PT8 · S1 · Q13 Five years ago, during the

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Five years ago, during the first North American outbreak of the cattle disease CXC, the death rate from the disease was 5 percent of all reported cases, whereas today the corresponding figure is over 18 percent.

Conclusion (it is clear / therefore)

CXC has increased in virulence over the past 5 years.

Evidence

The death rate from CXC was 5 percent of all reported cases five years ago during the first outbreak.

Today, the death rate is over 18 percent of reported cases.

Evaluate

This argument is an example of a correlation between time period and death rate being interpreted as evidence of increased virulence, making it fit the Explain Curious Fact pattern.

Curious Fact

Why has the death rate from CXC increased from 5 percent to over 18 percent?

Author's Explanation

CXC has increased in virulence (i.e. it's a more severe, deadly illness than before)

We'll mostly likely weaken this argument by proposing an Alternate Explanation for why the death rate has increased. Perhaps the data on reported cases isn't comparable across time periods; maybe there are other factors affecting the reporting and diagnosing of CXC.

We can also weaken by hurting the plausibility of the idea that the CXC has gotten more virulent.

Goal

Let's find an answer that suggests an Alternate Explanation for the increased death rate, or that tries to debunk the idea that CXC has gotten more virulent.

13.

Which one of the following, if true, most substantially weakens the argument?

  1. Many recent cattle deaths that

    Opposite (if anything)

    The idea that many recent cattle deaths from CXC have been misdiagnosed as another disease means there's even more death from CXC than we thought. That would if anything help the author argue, "See? CXC is getting so virulent." If this answer had said that a bunch of deaths that were from other causes were misdiagnosed as CXC, then that would have provided an alternate explanation for why the CXC death rate appears to have increased.

    20% picked this

  2. During the first North American

    No Impact

    If we were being told that the old death rate was misleadingly low then that could offer an alternate explanation for why the death rate seems so high now. But this answer is saying that the old death rate was misleadingly high.

    11% picked this

  3. An inoculation program against CXC

    No Impact

    This option discusses an inoculation program that just started, so it has nothing to do with debunking the idea that virulence has increased or offering an alternate explanation for the uptick in the death rate.

    7% picked this

  4. Correct

    Since the first outbreak, farmers

    Why this is right

    If farmers have learned to treat mild cases of CXC and no longer report them, then today's reported cases would be skewed towards more severe and likely fatal cases. This would explain the increased death rate without implying the disease itself has become more virulent, as mild cases aren't reflected in the statistics, leading to an apparently higher death rate among the reported cases.

    Skill tested: Weaken · how this choice captures the argument's function is the move to repeat next time.

    57% picked this

  5. Cattle that have contracted and

    No Impact

    This answer talks about disease recurrence, stating that cattle rarely contract CXC again after surviving it. This information doesn't affect the reported death rate's increase or undermine the increased virulence claim.

    4% picked this

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