PrepTest 118, Section 4, Question 19
According to some astronomers, Earth is struck by(64 more words not shown)
The reasoning in the argument(11 more words not shown)
- Amakes a bold(16 more words not shown)
- Bpresumes, without providing(29 more words not shown)
- Cmoves from evidence(19 more words not shown)
- Dfails to specify(18 more words not shown)
- Epresumes, without providing(13 more words not shown)
Reading the argument
An average isn't an appointment.
An event that happens once every 100 million years on average needn't arrive at exact 100-million-year intervals. Some gaps could be much longer, and others much shorter. We could even have two strikes close together and then a long period without one. The average alone doesn't tell us when the next strike is due.
Think of independent flips of a fair coin. Ten tails in a row don't make heads more likely on the next flip. The coin has no obligation to correct the recent run. Likewise, before treating a long gap between meteorites as evidence that the next one is coming soon, we'd need more than a historical average. We aren't given a schedule or a reason the waiting time increases the immediate risk.
I'd also want to know what protection research could accomplish and what work is already funded. But notice the actual proposal: fund an investigation into whether protection is possible. That doesn't promise an effective defense already exists.
What we’re looking for
For the flaw question, the clearest problem is the leap from average frequency to an imminent strike. The last strike occurring about one average interval ago doesn't establish that the next one will occur in the near future.
Working the answers
- A
A high probability of a disaster could give us a reason to take substantial action. The problem here comes earlier: the average-frequency evidence hasn't established the claimed near-term danger. A treats that high probability as established and objects to the recommendation on that basis, missing the unsupported prediction.
- B
This says the author assumes that the earlier timing does not affect the chance of the next event. The author is doing the opposite: the long time since the last strike is offered as a reason to expect another soon. Read the “not” carefully. B describes the assumption opposite to the one used in the prediction.
- CCorrect
The evidence concerns an average across intervals, while the prediction concerns when one particular future event will happen. We need some additional connection to move between those claims. Nothing given rules out another long wait or an irregular sequence of strikes.
“In the near future” is specific enough for this comparison. The author needn't name an exact date to go beyond the evidence: identifying the next strike as near is already more than the long-run average establishes.
- D
We could ask how likely a sufficiently large strike is to cause an ice age. But the argument's central mistake concerns whether a strike is expected soon. An exact estimate of the consequences wouldn't justify that timing prediction, and a potentially catastrophic impact could warrant concern without certainty about an ice age.
- E
The recommendation is to determine whether a means of protection exists. Research can be worth investigating without already knowing that it will succeed. The author doesn't have to assume a feasible defense has been found in order to propose looking for one.
More Flaw questions
Learn the LSAT our way
Our platform drills Flaw questions at your level and adjusts as you improve.