While it certainly is possible to get every question right on the SAT (with enough practice and hard work), for most of us, there will always be at least a few questions that leave us scratching our heads. When it comes to questions you aren’t sure about, you are bound to wonder: “Should I guess?” The answer it turns out is…it depends.

The SAT, unlike the ACT, wants to discourage test takers from guessing randomly on the test, so test takers are penalized a quarter of a point for every incorrect answer they submit. This means that if you have no idea which answer choices might be right, then you definitely shouldn’t try to guess.

But what if you can narrow it down somewhat? This is where it starts to get a little more complicated. Never fear – we can figure out when to guess and when not to guess with a little SAT level math. When it comes down to it, deciding when to guess is just a basic probability problem. You should guess when the probability of getting a question right is greater than 1/4 – that’s the quarter of a point you will lose if you get the question wrong.

Let’s think about it this way. There are five answer choices for every SAT multiple choice question. That means that if you are guessing completely randomly, you will have a 1 in 5 chance of getting it right. In other words, if you guess randomly on five questions, chances are you will get one right and the rest wrong.

How would this affect your score? You would lose 1/4 of a point for every wrong answer and gain a point for every right one:

Score = 1 – 1/4 – 1/4 – 1/4 – 1/4 = 0

Basically, on average it would be the same as if you hadn’t answered any of them at all. Thus, there is no advantage to guessing randomly.

But what happens if you can eliminate one answer choice? After all, there is usually at least one “throw away” answer choice on every question – one choice that is very obviously wrong. Now you have four answer choices left to choose from, so if you guess randomly after eliminating one answer choice you will have a 1 in 4 chance of getting it right. This means that if you guess on four questions after eliminating one answer choice from each of them, chances are you will get one of them right and the other three wrong:

Score = 1 – 1/4 – 1/4 – 1/4 = 1/4

After guessing on four such questions you end up coming out ahead by a quarter of a point. Thus, technically, there is an advantage to guessing on the SAT as long as you can eliminate at least one answer choice from each question you guess on.

The more wrong answer choices you can eliminate, the better the odds become, and the more advantage there is to guessing. If you can eliminate two wrong answer choices, then you have a 1 in 3 chance of getting the question right. Thus, if you guess on three such questions, your score would likely be:

Score = 1 – 1/4 – 1/4 = 1/2

You come out ahead by half a point. If you can narrow your choice down to only two answers by eliminating the other three, then you now have a 50/50 chance of getting it right. So, if you guess on two such questions:

Score = 1 – 1/4 = 3/4

You come out ahead by 3/4 of a point.

So, when should you guess? At College Compass, we recommend that you guess whenever you can eliminate at least two answer choices. Even though there is technically an advantage to guessing after eliminating only one answer choice, we recommend skipping these questions rather than guessing on them. This is because you have to remember that in all of the calculations above, we are talking about *average* probabilities. This means that the more times a probabilistic even occurs, the more closely the actual outcomes will resemble the average probability. If the number of probabilistic events is small, then the actual outcomes could easily vary significantly from the predicted outcomes.

For instance, you know perfectly well that if you toss a coin, it is quite plausible that you could get heads twice in a row, even though there is a 50/50 chance of getting heads. If you toss the coin a hundred times, though, chances are that about 50% of the time you will have gotten heads. If you toss the coin a thousand times, then the actual outcomes will be even closer to 50% heads, 50% tails.

Hopefully, you won’t be guessing on *that* many questions on the SAT, so even though you do have a one in four chance of getting a question right after eliminating only one answer choice, you could very easily guess on four questions like that and get them all wrong, just as you could easily toss a coin and get heads twice in a row. Thus, we recommend improving your odds by only guessing when you have eliminated at least two answer choices.

Hopefully, that should answer your questions about when to guess and when not to guess. Remember, Test Masters is always available to answer all your test prep questions and to give you the edge you need to do your best on the SAT, ACT, and all your college admissions exams. Until next time, keep up the good work, and happy studying!