Negative marking is a skill, and almost nobody teaches it

Ask a student who has just come out of a JEE mock how it went and you will often hear a version of the same sentence. They left about twenty blank because they were not sure, and they think that was the safe thing to do.

Under plus four minus one, it was not. Leaving those twenty blank cost them marks against almost any reasonable estimate of what they knew. The student was being careful, and careful was the expensive option.

The arithmetic almost nobody is shown

A guess is worth making when its expected value clears zero. Under a scheme that awards c for a right answer and takes w for a wrong one, an attempt with accuracy a returns

expected marks = a × c minus (1 minus a) × w

Set that to zero and solve, and the break even accuracy is w divided by (c plus w). Nothing about that depends on the student, the subject or the difficulty of the paper. It falls straight out of the marking scheme.

Run the four schemes an Indian student is likely to meet:

• JEE Main and JEE Advanced single correct, plus four minus one. Break even at twenty per cent. Guess whenever you can do better than one in five.
• NEET, plus four minus one. Also twenty per cent.
• BITSAT, plus three minus one. Twenty-five per cent, and the bonus round changes what that number is worth.
• CLAT, plus one minus a quarter. Twenty per cent again.

Twenty per cent is one option in five. On a four option paper, blind guessing sits at twenty-five per cent, which already clears the bar. The moment you eliminate a single option you are at thirty-three per cent and comfortably ahead.

So why does everyone believe the opposite

Because the feedback a student gets is lopsided. A wrong answer arrives with a visible penalty attached, printed in red, subtracted in front of them. A blank arrives with nothing. The cost of the blank is invisible, because it is a mark that never appeared rather than one that was taken away.

Teachers reinforce it without meaning to. Telling a class not to guess is a reasonable instruction if what you mean is do not answer at random on questions you have not read. It gets heard as do not answer unless you are sure, and those are wildly different instructions.

Then there is the student's own temperament. In our own sittings the students who leave the most blank are rarely the careless ones. They are conscientious, they dislike being wrong, and they have quietly decided that a blank is honest while a guess is a kind of cheating. That belief costs them more marks than any topic they never revised.

Where the rule genuinely does not apply

Three places, and they matter.

Numerical entry questions. Typing a value you have not derived is not a one in four proposition, it is closer to one in several thousand. On JEE Main these now carry the same minus one as the multiple choice questions, so an untethered guess is a straightforward loss. If your working produced a number, enter it. If it did not, leave it.

Multiple correct questions in JEE Advanced. The marking punishes partial recklessness specifically, and it is a large part of why accuracy falls between the Mains and Advanced halves of a sitting. Selecting every option you think might be right, when one of them is wrong, drops you to minus two from a possible plus four. Mark only the options you can defend, take the partial credit, and stop.

Papers with no negative marking at all. NATA has none. The Short Answer section of IPMAT Indore has none either. On those, leaving anything blank is pure loss and there is no argument to have.

What to do about it in a fortnight

Sit one paper under a real clock and mark it two ways. Once as you actually answered it. Once as you would have scored had you attempted every question where you could rule out at least one option. The gap between those two numbers is what your guessing policy is currently costing, and for most students it is between eight and twenty marks.

Then practise the elimination itself, because that is the skill underneath the arithmetic. Not solving faster. Deciding faster whether an option can be ruled out. A student who can knock out one option in fifteen seconds on a question they cannot solve has turned a blank into a positive expected return, and there are twenty of those on a paper.

The uncomfortable part

Attempt strategy is one of the few things in entrance preparation that can be corrected in an afternoon. Almost nothing else can. Which is precisely why coaching institutes spend so little time on it: there is no eighteen month course to sell in a rule you can explain in ten minutes and practise in two hours.

It also means that a student whose mock scores jump after a session on guessing policy has not become better at Physics. Their real position is unchanged. That is worth remembering before anyone concludes the coaching is working.

Our LENS readiness checks report attempt strategy as a separate number from subject knowledge, precisely so the two do not get confused with each other. The report will tell you how many marks went back to wrong answers on topics where the student was below break even, and how many were left on the table by blanks that were worth attempting. Those are different problems with different fixes, and adding them together helps nobody.