Logical reasoning PrepTest 126 · Section 1 · Question 9

Incorrect. If the changes in electric currents do, in fact, presage an earthquake, then it doesn't matter if scientists understand how these phenomena are related. It therefore doesn't weaken the argument to say scientists don't understand it. It'd be like saying that since you don't understand how your microwave works, it can't heat your food.

Incorrect. If the correlation between this method and earthquakes is stronger than other methods, that would only serve to strengthen the use of this over those methods.

Incorrect. Without knowing if the frequency of electric current changes, we can't tell how this affects the argument.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Weaken

Stimulus Summary:
Before each recent earthquake, a change in the earth's electric current was detected, so using this will better help to predict earthquakes/evacuate towns.

Answer Anticipation:
This argument falls into a less common pattern on the LSAT, but one you should be aware of.

This argument tries to use the correlation between two phenomena to use one to predict the other. Despite the correlation, it would be easy to determine this isn't related to a correlation/causation flaw because the argument doesn't reach a causal conclusion—it doesn't state that the electrical current causes the earthquake.

However, it does assume causality. While it doesn't present a causal relationship between the prediction factor (electric current changes) and the event (earthquake), it assumes that something is causing both of them—that's the only way it makes sense to use one to predict the other.

When an argument is making such an argument/assumption, there are two key things to consider:
(1) Is the prediction factor absent when the cause doesn't happen? If these changes in the electric current of the earth also happen many times when an earthquake doesn't, then they're not actually a good prediction. This argument could be weakened if that's the case (think of this as you would a Control group in a correlation/causation flaw question).
(2) Does the timeline match up? If the electric currents change at varying times before an earthquake, then the correlation is much weaker. (If, on the other hand, they always happen 2 hours before the earthquake, then the correlation is much stronger.)

Answer Explanation:
This answer deals with the second issue from our anticipation. If the electric currents change before earthquakes, but it's at varying times, then there's a much weaker correlation between the two phenomena and using the former to predict the latter doesn't appear to be all that accurate. If two phenomena are causally related (even if via a third cause), then there should be a relatively standard "lag time" between the cause and effect.

Key Takeaway:
A less common, but still frequent enough to mention, argument type will establish that one thing predicts another based on a correlation between them. This type of causal relationship generally has one of two issues:
(1) It doesn't analyze counterexamples, or establish a control—does the predicting phenomenon happen only when and every time the predicted phenomenon happens?
(2) What's the lag time? If something is going to predict another, then there should be a standard amount of time between the first phenomenon and the second.

Incorrect. First, more stations could potentially be built. Second, one station may be enough to detect all the changes needed to make predictions throughout the region.