In this post, I explain why blind guessing on the SAT is a bad idea. Now we will talk about why guessing is a bad idea even if you have eliminated one answer. Technically, you should have a slight mathematical advantage by then – and yet, almost every student who applies this finds themselves still losing points. There are a few key reasons why this happens.

1. The calculations are based on ignoring the rounding effect. They treat getting 1 right and 3 wrong as a quarter point gain. In reality, an outcome of 1 right and 3 wrong is NOT a gain of a quarter point because your score will be rounded down. This is another situation where your most likely outcome (at about 42%) is no harm and your next most likely outcome (at about 31%) is getting all 4 wrong and harming your score.

2. If you can only eliminate one, that probably means the question is very hard for you. Which means the possibility that you will eliminate the correct answer just went up (since obviously that’s more likely to occur on a difficult question). Once that has happened, you have 0% chance of getting the question right, 100% guarantee of a lost quarter point, and any additional time spent on that question is wasted.

3. Even if you correctly eliminate one wrong answer, you don’t have a true 1 in 4 chance of guessing the right answer. To understand this part, consider the street game 3 Card Monty (we will modify it slightly to fit our scenario of guessing with 4 answers left). A dealer shows you four cards, one of which is a Joker and 3 of which are pip cards (numbered cards). They offer to bet with you. If you can select the Joker card after they place all 4 face down and shuffle them briefly, you will win a fantastic payoff worth far more than your wager! You rub your hands together greedily, knowing the payoff is worth more than you are betting, and confident that with a 1 in 4 chance you can win enough to make this game worthwhile. The dealer shuffles, you watch the cards and pick, confident you saw where that Joker landed. WHAT?!? You stare in amazement; the card you picked is NOT the Joker. You demand to see the cards turned over, sure that the dealer must have slipped the Joker off the table or into a sleeve. But no, it’s right there on the table, just not where you thought it was. Hmm, well that payoff is still good, good enough to risk another bet and you are going to pay *real* close attention this time. The dealer shuffles… and sure enough, you lose again. You keep guessing wrong, all the while losing confidence, time and money, while that smug bastard laughs at you.

Now let’s look at why you didn’t win 1 in 4 times, or anything close to it. The dealer doesn’t need to cheat – it is his extensive experience at shuffling deceptively, distracting you and knowing how people react to his game that gives him a strong advantage. He makes a living doing this – you are just wandering by. You are, no matter how smart and no matter how well trained, a teenager being sent into a battle of wits in very specific areas with people who have advanced degrees and years of experience in the fine art of making you guess wrong. If you can only eliminate one answer, the chances that one of those trap answers will suck you in rises to a point where your real odds are no longer 1 in 4.

Finally, let’s consider the big picture. Even if you ignore the rounding effect, and feel 100% sure you won’t eliminate the right answer and will guess without being even slightly affected by any of the 3 remaining trap answers, it still won’t work out overall. Think about it realistically – will you really say ‘ok, I got rid of one, I’ll guess now and move on.‘? Of course not. You know eliminating more would improve your odds further, so you will sit there staring at the remaining ones hoping to find a reason to get rid of more. Meanwhile the clock is ticking, other questions never get tried because time ran out and the Joker is just sitting there, grinning at you evilly.

Don’t let him get away with it. Be strong enough and smart enough to refuse to play his game until the odds really are in your favour. Walk away from those harder ones and go knock out some easier questions instead!