Roberta is irritable only when

Answer choices

1. A

   Not Causal17% picked this

   infers from a correlation between tiredness and yawning that tiredness

   This answer describes one of the 10 famous flaws, Causal, in which the author overconfidently assumes a causal relationship between two things that were correlated in the premise. Whenever an answer says "infers from X that Y", then X should match evidence and Y should match a conclusion the author drew. Did the author conclude that "tiredness causes yawning"? Nope. There also wasn't a correlation between tiredness and yawning presented (that would have sounded like, "People who are frequently tired are more likely than those who aren't to yawn").

   17%
2. B

   Not Circular6% picked this

   assumes the conclusion that it sets out

   This answer describes one of the 10 famous flaws, Circular Reasoning, in which the premise restates the conclusion or requires the truth of the conclusion. This answer is almost always wrong. The conclusion here is that Roberta is irritable, and none of the premises require that she is currently irritable.

   6%
3. C

   Not Sampling3% picked this

   generalizes on the basis of a

   This answer describes one of the 10 famous flaws, Sampling, in which we critique the argument for using a sample that is too small, unrepresentative, or biased in some way. This argument doesn't use any sample at all.

   3%
4. D

   Not the Broken Conditional19% picked this

   takes a necessary condition for Roberta's losing things to be a

   There were two conditionals but the author only interpreted one of them illegally, and it was the one about being "irritable" not about "losing things". The "losing things" conditional was: If R loses something, then she's tired The premise establishes that Roberta did lose something (her keys), and so according to this rule she is tired. There's nothing wrong with thinking that. The problem is that the author thinks, "If she's tired, she must be irritable".

   19%
5. E

   Correct55% picked this

   takes a necessary condition for Roberta's being irritable to be a

   Why this is right

   This points to the conditional that the author interpreted backwards. Because Roberta lost her keys, we know that she is tired. But her being tired doesn't prove she's almost certainly irritable. In order for Roberta to be irritable she has to be tired (it's necessary for her to be irritable). But being tired isn't sufficient to show she's irritable. She might be really good at being tired but not getting cranky.

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

   55%