Choosing the Least Incorrect Answer


My son was complaining to me the other day that he missed on question on a multiple choice quiz in his class and he got a low B grade instead of getting a perfect score. When I asked him why he was frustrated he told me, “Because it was easy and I missed it. But I think the question was wrong.” As usual, I pressed him further to explain his reasoning and found out that the question was indeed ambiguous but the answer choices were pretty obviously wrong all over. He asked me why someone would write a test like that. Which is how he got a big lesson on writing test questions.

Spin the Wheel

When you write a multiple choice test question for any reputable exam you are supposed to pick “wrong” answers, known as distractors, that ensure that the candidate doesn’t have a better than 25% chance of guessing the correct answer. You’ve probably seen this before because you took some kind of simple quiz that had answers that were completely wrong to the point of being easy to pick out. Those quizzes are usually designed to be passed with the minimum amount of effort.

This also extends to a question that includes answer choices that are paired. If you write a question that says “pick the three best answers” with six options that are binary pairs you’re basically saying to the candidate “Pick between these two three times and you’re probably going to get it right”. I’ve seen a number of these kinds of questions over the years and it feels like a shortcut to getting one on the house.

The most devious questions come from the math side of the house. Some of my friends have been known to write questions for their math tests and purposely work the problem wrong at a critical point to get a distractor that looks very plausible. You make the same mistake and you’re going to see the correct answer in the choices and get it wrong. The extra effort here matters because if you see too many students getting the same wrong distractor as the answer you know that there may be confusion about the process at that critical point. Also, the effort to make math question distractors look plausible is impressive and way too time consuming.

Why Is It Wrong?

Compelling distractors are a requirement for any sufficiently advanced testing platform. The professionals that write the tests understand that guessing your way through a multiple choice exam is a bad precedent and the whole format needs to be fair. The secret to getting the leg up on these exams is more than just knowing the right answer. It’s about knowing why things are wrong.

Take an easy example: OSPF LSAs. A question may ask you about a particular router in a diagram and ask you which LSAs that it sees. If the answer choices are fairly configured you’re going to be faced with some plausible looking answers. Say the question is about a not-so-stubby-area (NSSA). If you know the specifics of what makes this area unique you can start eliminating choices from the question. What if it’s asking about which LSAs are not allowed? Well, if you forgot the answer to that you can start by reading the answer choices and applying logic.

You can usually improve your chances of getting a question right by figuring out why the answers given are wrong for the question. In the above example, if LSA Type 1 is listed as an answer choice ask yourself “Why is this the wrong answer?” For the question about disallowed LSA types you can eliminate this choice because LSA Type 1 is always present inside an area. For a question about visibility of that LSA outside of an area you’d be asking a different question. But if you know that Type 1 LSAs are local and always visible you can cross off that as a potential answer. That means you boosted your chances of guessing the answer to 33%!

The question itself is easy if you know that NSSAs use Type 7 LSAs to convey information because Type 5 LSAs aren’t allowed. But if you understand why the other answers are wrong for the question asked you can also check your work. Why would you want to do that? Because the wording of the question can trip you up. How many times have you skimmed the question looking for keywords and missing things like “not” or “except”? If you work the question backwards looking for why answers are wrong and you keep coming up with them being right you may have read the question incorrectly in the first place. Likewise, if every answer is wrong somehow you may have a bad question on your hands.

What happens if the question is poorly worded and all the answer choices are wrong? Well, that’s when you get to pick the least incorrect answer and leave feedback. It’s not about picking the perfect answer in these situations. You have to know that a lot of hands touch test questions and there are times when things are rewritten and the intent can be changed somehow. If you know that you are dealing with a question that is ambiguous or flat-out wrong you should leave feedback in the question comments so it can be corrected. But you still have to answer the question. So, use the above method to find the piece that is the least incorrect and go with that choice. It may not be “right” according to the test question writer, but if enough people pick that answer you’re going to see someone taking a hard look at the question.


Tom’s Take

We are going to take a lot of tests in our lives. Multiple choice tests are easier but require lots of work, both on the part of the writer and the taker. It’s not enough to just memorize what the correct answers are going to be. If you study hard and understand why the distractors are incorrect you’ll have a more complete understanding of the material and you’ll be able to check your work as you go along. Given that most certification exams don’t allow you to go back and change answers once you’ve moved past the question the ability to check yourself in real time gives you an advantage that can mean the difference between passing and retaking the exam. And that same approach can help you when everything on the page looks wrong.

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