A letter submitted to the editor

Answer choices

1. A

   Different Flaw6% picked this

   Since 19 out of 20 home computers are purchased primarily for use with computer games, and the first computer sold today was purchased solely

   At first, seeing the same 19 out of 20, we could be thinking, "Superficial similarity trap! They're just trying to bait me with the same fraction / ratio". But glancing down the answers, we see that all of the answer choices are still playing with the 5% / 95%, or 1/20 to 19/20 split. This argument is flawed because it interprets the 19 out of 20 too literally. It thinks that a past data point (we got the 1 word processing computer out of the 20) influences how the forthcoming data points will go. If we know that certain storms only occur once every 60 years, and we have that type of storm in 2020, we're not allowed to conclude that the next storm will be in 2080. That's interpreting an average rate too literally. The original argument wasn't guilty of interpreting an average rate too literally, based on some data point. It was guilty of ignoring a 2nd fact we had (female name) that might affect or supersede our other means of estimating probability (overall rate of females / males in that professional role).

   6%
2. B

   Different Flaw6% picked this

   Fewer than 1 in 20 of the manuscripts submitted to Argon Publishing Co. are accepted for publication. Since only 15 manuscripts were submitted last

   Just like (A), this argument is flawed because it interprets an average rate too literally. It thinks that if the rate of acceptance is less than 1 in 20, then there's no chance you get an accepted one until you get to at least 20 manuscripts. We can't accuse this argument, as we can with the original, of failing to consider how some known fact might supersede the probability statistic we're using.

   6%
3. C

   Bad Conclusion Match6% picked this

   Fewer than 5 percent of last year’s graduating class took Latin in secondary school. Howard took Latin in secondary school, so if he had

   This conclusion is a conditional, and it also almost sounds causal. It sounds like it's saying, "If X had happened, it would have caused Y". That bears no resemblance to our actual conclusion, which is just saying, "There's a better than 19/20 probability that the letter was written by a man".

   6%
4. D

   Different Flaw13% picked this

   More than 95 percent of the planes built by UBC last year met government standards for large airliners. Since small planes account for just

   It's hard to even understand the argument this is trying to make, but let's use some specific numbers to try: UBC is an airliner. 4% of the planes they built last year were small. (So 96% of the planes they built were large) 96% of the planes they built met government standards. So, all of the large planes met government standards. The author is thinking since "more than 95%" matches the percent that met standards and "more than 95%" matches large planes, that those two things must be a perfect overlap. But the argument fails to consider that UBC may have had this breakdown: 4%, small + meets standards 92%, large + meets standards 4%, large + doesn't meet standards That would fit the evidence (96% meet standards) but not the conclusion (all the large ones meet standards). But this is not the same flaw as "ignoring a fact that should supersede your probability argument".

   13%
5. E

   Correct69% picked this

   Since more than 19 out of every 20 animals in the wildlife preserve are mammals and fewer than 1 out of 20 are birds,

   Why this is right

   This replicates the "Shirley" flaw. If we were just going off population numbers, then, yes, the probability that what Emily saw was a mammal would be greater than 95%, because mammals are more than 19 out of 20. But the fact that the mammal was flying seems like it should shake up our default probability. That is a strong context clue that what she saw is probably a bird, just as Dr. Shirley Martin is a strong context clue that the person who wrote the letter is probably female.

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

   69%