NEET UG gives +4 marks for a correct answer, −1 for a wrong answer and 0 for a question left unanswered. So every time you are not sure, you face a small bet: answer and risk losing a mark, or leave it and score nothing.
There is a simple way to decide, and it comes from basic probability.
The idea: expected marks
The expected value of a guess is what it is worth on average if you made the same kind of guess many times:
(chance right × 4) − (chance wrong × 1)
Leaving a question blank is always worth exactly 0. So a guess is worth making, on average, whenever its expected value is above 0.
A blind guess: +0.25
With four options and no idea which is correct, your chance of being right is 1 in 4.
0.25 × 4 − 0.75 × 1 = 1 − 0.75 = +0.25
So even a blind guess is slightly positive on average. But it is the weakest bet you can make: three times out of four you lose a mark.
Rule out one option: +0.67
If you can prove one option wrong, three remain and your chance becomes 1 in 3.
(1/3) × 4 − (2/3) × 1 = 1.33 − 0.67 = +0.67
One elimination makes the guess more than two and a half times as valuable.
Rule out two options: +1.5
With two options left, it is a 50–50.
0.5 × 4 − 0.5 × 1 = 2 − 0.5 = +1.5
That is six times the value of a blind guess.
| Options left | Chance right | Expected marks |
|---|---|---|
| 4 (blind guess) | 1 in 4 (25%) | +0.25 |
| 3 (one ruled out) | 1 in 3 (33%) | +0.67 |
| 2 (two ruled out) | 1 in 2 (50%) | +1.5 |
| Left blank | — | 0 |
The break-even point: 20%
Set the expected value to zero and solve: chance × 4 = (1 − chance) × 1, so the chance is 1 in 5, or 20%.
In other words, a guess pays on average whenever your real chance of being right is above 20%. That is the number to remember.
The catch: time, and false confidence
The maths ignores two things.
Time. Every minute spent stuck on one question is a minute taken from questions you could actually solve. A question you can answer with confidence is worth +4, far more than any guess. Don't let a guess eat the time for one of those.
Wrong eliminations. The numbers above assume the options you ruled out really are wrong. If you cross out the correct answer, your chance on that question drops to zero. Eliminate only when you can say why an option is wrong, not just that it "looks wrong".
Remember too that expected value is an average over many questions. On any single question you either gain 4 or lose 1. Over a full paper, the averages are what decide your score.
The habit: eliminate first, then decide
- First pass: answer every question you are sure about. Mark the rest and move on.
- Second pass: on each marked question, cross out every option you can prove wrong.
- Decide: with two options left, or three with real reasons, answer. With nothing ruled out, a guess is still slightly positive on paper, but it is the riskiest choice, so leave it for the very end and only if time remains.
Practise it before the exam
Treat guessing as a skill you train, not a decision you make in panic. In each practice test, mark every question you answered after eliminating options. Afterwards, count how many of those you got right.
If your hit rate on those questions is comfortably above 20%, your eliminations are working and guessing is earning you marks. If it is close to or below 20%, your eliminations need work, and the fix is more chapter practice, not more guessing.