Roberta is irritable only when she is tired, and loses things only when she is tired. Since she has been yawning all ...

ChristianJM on March 23, 2020

Please explain answer

I thought the answer was D I narrowed it down to these two but found D correct clearly it is E. Please explain why.

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SamA on March 23, 2020

Hello @ChristianJM,

1. Roberta is irritable (RI) only when she is tired (RT).

RI ----> RT

2. Roberta loses things (RL) only when she is tired (RT).

RL ---> RT

We are then told that Roberta has lost her keys. Based on the second premise, we can indeed confirm that she is tired. The author has correctly understood that losing things is sufficient for tiredness. We know for a fact that she lost something, so the author is not assuming that she did just because she yawned. This is why D is not the flaw.

However, the author then uses tiredness to conclude irritability. This is the mistake, as the author has reversed the conditions of our first premise. She concludes that tiredness is sufficient for irritability, which is not the case. Answer choice E best describes the flaw.