Errors in Reasoning Questions - - Question 56

A standard problem for computer security is that passwords that have to be typed on a computer keyboard are comparati...

marissa July 19, 2018

Why is D correct

I have read the explanations for why D is correct and why A and B are incorrect, but I am still not entirely convinced. I understand that the evidence fails to rule out the possibility that the system may sometimes deny access to people that are entitled access, but I still don't see why that is a flaw in the argument. Even if people that are entitled to access are sometimes denied, the conclusion that there will be a way of giving access to those people who are entitled to access and to no one else could still hold, so long as the only people being given access are those entitled to it, even if not all of the people entitled to access are given it. I'd appreciate some clarification, and thank you in advance.

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Anita July 20, 2018

@marissa The catch here is "giving access to those people who are entitled to access." There's nothing in the prompt it didn't say that it's any good at granting people access, only that it's very good at not granting people access. Maybe it hardly works at all, and therefore it's not good at avoiding the problems and granting access.

marissa August 9, 2018

Ok but that still doesn't answer my question. That's exactly what the explanation says, but the answer says it sometimes denies access to people who are entitled to it, so my initial problem still holds. I don't understand why that's a flaw in the argument because even if the system sometimes fails to grant access to those entitled it could still ONLY grant access to those entitled to it, even if it doesn't all of the time. I don't really see how I'm wrong ?

Anita August 9, 2018

@marissa What we’re looking for is a flaw in the reasoning. The conclusion is that the test in an operational setting will (a) give access to those entitled and (b) not give access to others. However, the prompt never says that the test ever did give access to those entitled. So we cannot conclude (a) from the results. We would need something in the prompt to say that the test never incorrectly granted access and at least sometimes, or hopefully always, granted correct access. However, without this data, the conclusion is flawed. That’s what we’re looking for.

A says that the problem is that it would suffer from the same issues, which doesn’t appear to be the case here, since we know it doesn’t grant faulty access.

B says it bases its conclusion on too little data, but we don’t actually know the size of the tests, so it could very well be legitimate.

D says it could deny access to those who need it. This is the flaw we pointed out about (a).

Did I get everything you were looking for?