The National Association of Fire

Answer choices

1. A

   Irrelevant Quality5% picked this

   Fifteen percent of domestic smoke detectors were installed less than 10

   The argument is just about whether we have more functioning smoke detectors now compared to 10 years ago. When these smoke detectors were installed doesn't make any difference to that calculation. We only care about what proportion of homes have smoke detectors and what proportion of those smoke detectors are operable vs. inoperable. If we negate this and say that some other % of smoke detectors were installed in the past ten years, it doesn't change or hurt the argument at all. This answer is just baiting people with 45% - 30% = 15%

   5%
2. B

   Irrelevant Comparison10% picked this

   The number of fires per year in homes with smoke detectors

   The number of fires per year and their relation to homes with smoke detectors does not address the operability of the detectors, which is the main concern in whether early detection is more likely. The argument isn't about actual fires going up or down. It's about whether the proportion of homes with functional smoke detectors has gone up or down.

   10%
3. C

   Irrelevant Quality7% picked this

   Not all of the smoke detectors in homes are

   It doesn't matter whether 100% of smoke detectors are battery operated or less than 100%. We just care about whether or not they're in operable condition, however it is that they get their power. This is baiting people into inferring from "inoperable because of no batteries or because of some other reason" that some detectors don't use batteries. That's not a valid inference (also not our task on Necessary Assumption). A battery-powered smoke detector can be inoperable for some other reason, such as maybe it got smashed by a basketball and some of its internal circuits have come apart.

   7%
4. D

   Correct71% picked this

   The proportion of domestic smoke detectors that are inoperative has increased in the

   Why this is right

   This gets to the Assumed Difference. If ten years ago we had the same proportion of inoperable smoke detectors (we'll say 50%), then we would currently have more operable smoke detectors than ten years ago, which basically contradicts the conclusion. 50% of 30% is 15%. So ten years ago 15% of homes would have had operable smoke detectors. And 50% of 45% is 22.5%. So now 22.5% of homes would have operable smoke detectors. The author's argument only makes sense if we interpret the "over half are inoperable" premise as a NEW problem. He has to be arguing that "even though a larger proportion of homes have these detectors, there's this new problem where tons of them are inoperable, so that offsets the gain in detectors and leaves us essentially where we were ten years ago."

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

   71%
5. E

   Irrelevant Comparison8% picked this

   Unlike automatic water sprinklers, a properly functioning smoke detector cannot by itself increase fire safety

   This argument is only about smoke detectors, so we don't have to assume anything about sprinklers. If we negated this and go "a properly functioning smoke detector can by itself increase fire safety", it wouldn't weaken. The author agrees that FUNCTIONING smoke detectors increase safety. Her argument is about how inoperable detectors mean we aren't getting an increase in safety.

   8%