Logical Reasoning

PT154 · S2 · Q21 A study of 30 years

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A study of 30 years of weather pattern records of several industrialized urban areas found that weekend days tend to be cloudier than weekdays.

Conclusion

It's now undeniable that humans have an effect on the weather.

Evidence

A study of 30 urban cities found that weekends were cloudier than weekdays.

There are a few 7 day cycles in nature, but none of them could have this big an effect on weather.

Evaluate

This is a Curious Fact / Explanation type template.

Curious Fact ... How come in this study, the weekends were cloudier than the weekdays?

Author's Explanation ... Humans are causing it. (Humans are causing noticeable changes to weather on a large scale)

Since the weekend/weekday thing reminds us of a 7 day workweek, and since they're observing this "weekends are cloudier than weekdays" correlation, the author thinks that humans are causing this.

She considers whether there are any natural explanations for this "weekends are cloudier than weekdays" phenomenon but rules them out because the only 7 day cycles that exist are too puny to affect large scale weather.

We are thinking - Is there some OTHER WAY to explain the curious fact? - Is the AUTHOR'S WAY plausible?

The author is definitely assuming a difference:

Necessary Assumption + Curious Fact usually means "ruling out an alternate explanation".

How else could we explain the "cloudy weekends" phenomenon? There are no natural explanations that are 7 day cycles.

Could it be a 14 day cycle, or a 28 day cycle like the lunar cycle?

Goal

Look for an answer that needs to be true for it to be plausible that human activity is causing these cloudy weekends, or an answer that rules out an alternate explanation for cloudy weekends.

21.

Which one of the following is an assumption on which the argument depends?

  1. Industrial activity tends to decrease

    Too Strong: tends to / significantly

    The author doesn't necessarily need to think that industrial activity drops off a ton on the weekends. It's not common sense that "factories not running as hard = cloudier days". And the author could think that something else about the 7 day workweek is the causal factor. Maybe factories run constantly all week, but driving patterns are very different on the weekends.

    25% picked this

  2. There are no naturally occurring

    Out of Scope: in the area

    The author is saying there are only a few 7 day cycles in nature, but none of them could plausibly explain a large scale weather pattern, so they're all non-starters as explanations. Since none of them are eligible to be the explanation, it really doesn't matter whether they occur here or there.

    7% picked this

  3. If living organisms have an

    Bad Premise/Conclusion Match

    When answer choices are conditional on Necessary Assumption, think about how they would be diagrammed, and ask yourself if they're replicating a Premise to Conclusion move that the author made. Living orgs have appreciable at least partly large-scale effect on weather → due to humans Did the premise establish that living organisms have an appreciable large-scale effect on weather patterns? No, that's mostly wording from the Conclusion, not from the Premise. The premise is just a study which finds a correlation and the author ruling out any natural 7-day cycle. The author might well disagree with this answer choice. The fact that she searched her mind for a potential natural way of explaining the cloudy weekends mystery suggests that she might be totally tolerant of explaining an appreciable large-scale effect on weather. She ruled out 7-DAY natural cycles, but she might accept that there are lots of non-human examples of living organisms having a big effect on weather patterns.

    24% picked this

  4. If something appreciably affects large-scale

    Bad Premise/Conclusion Match

    Again, we have a conditional that we can look at and see if it matches the flow of the argument: X appreciably affects → probably cyclical large-scale weather Was there a premise that said that something was appreciably affecting large scale weather? No. That was the Conclusion. The author is assuming that "If there is a correlation like cloudy weekends, it is probably caused by a 7 day cycle"

    12% picked this

  5. Correct

    If a weather pattern with

    Why this is right

    Again, we can look at this conditionally and ask if it matches. Weather pattern Cause has w/ natural cause → 7 day cycle has a 7 day cycle This is a brutal correct answer. It doesn't represent a Premise to Conclusion move, but it does represent something the author is thinking behind the scenes. The "cloudy weekends" correlation from the study is a seven day weather pattern. The author is wondering whether it's caused by humans or something "natural". He rules out the possibility of "natural" by saying that there are no 7-day natural cycles that could possibly be contenders. But why is he limiting himself to considering 7-day cycles? Why does he assume that in order for a natural cause to account for this 7-day "cloudy weekends" weather pattern, that the natural cycle would have to be 7 days? Were we to negate this answer, it would give us the space to say "a natural cause for this doesn't necessarily have to be a 7 day cycle! What about a 14 day cycle?" So we can think of this answer as reflecting a reasoning move the author made, or we can think of it as ruling out Alternate Explanations for the curious fact (the cloudy-weekend thing is not caused by some natural 14 day cycle).

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

    30% picked this

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