Negative marking and accuracy in SBI PO

Two candidates can know exactly the same answers and walk out with scores several marks apart. The difference is what they did with the questions they were not sure about. In SBI PO, where the prelims is decided on aggregate marks and the mains has a cut-off in every section, those few marks decide who moves on.

This guide sets out the rule, works through the arithmetic of guessing, shows why the mains changes the stakes, and ends with a routine for raising your accuracy in mocks.

The rule

In both objective tests, one-quarter of the marks assigned to a question is deducted for each wrong answer. A question you leave blank costs nothing. The descriptive paper has no negative marking; it is marked on what you write.

Because mains sections carry different marks per question, the penalty changes from section to section:

The last column is the one to remember. A careless error on a question you could have solved costs you the marks you did not earn plus the penalty. One slip in DI costs 2.5 marks, which is the same as four careless English errors.

The arithmetic of a guess

Bank exam questions usually have five options. Take a question worth m marks.

• Correct: +m
• Wrong: −m/4
• Blank: 0

The expected value of attempting is (chance right × m) − (chance wrong × m/4). Work it through for each situation you meet in the hall:

Two conclusions follow, and they hold whatever the marks per question:

1. A blind guess gains nothing on average. It does not lose on average either, but it widens the spread of your possible scores. In a section with a cut-off, that spread is a risk you do not need.
2. Every option you can honestly rule out turns a guess positive. The break-even point is a 20% chance of being right. Any real knowledge pushes you above it.

Why "honestly" matters

The table assumes your eliminations are correct. If you cross out the option that was actually right, your "fifty-fifty" was really a zero. Candidates lose marks this way all the time: they eliminate on a hunch, then treat the question as safe. A genuine elimination has a reason you could state, such as a unit that cannot be right, a calculation that rules out a range, or a grammar rule the option breaks.

Time is the other cost

Expected value ignores time, and time is short: 30 seconds a question in prelims English, about 40 seconds in prelims quant and reasoning. A question you spend two minutes narrowing to two options may have been worth less than two fresh questions you never reached. Guess quickly once you have eliminated, then move on.

Accuracy beats attempts

With the one-quarter rule, your net score is correct answers minus a quarter of wrong ones. Extra attempts only help if they come with enough accuracy.

Worked example (prelims, 1 mark each). These are made-up figures to show the arithmetic.

Candidate B attempted six fewer questions and finished 2.75 marks ahead.

Worked example (mains DI, 2 marks each). Suppose a candidate attempts 18 DI questions and gets 15 right: 15 × 2 − 3 × 0.5 = 30 − 1.5 = 28.5. In the next mock they push to 24 attempts but get only 16 right: 16 × 2 − 8 × 0.5 = 32 − 4 = 28. Six more attempts produced one more correct answer and a lower score, and cost several minutes that could have gone to checking.

Where the stakes are highest

Treat each mains section by its marks:

• DI (2 marks): the most expensive place to be careless. Re-read which year, row or unit the question asks for before you calculate.
• Reasoning (1.5 marks): a puzzle answered from an unfinished diagram can cost five questions at once. Answer only when every clue has been checked.
• Awareness (1 mark): you usually know it or you do not. Elimination works on dates, bodies and schemes you partly remember; blind guessing on a name you have never seen does not.
• English (0.5 marks): penalties are small, but the section has its own cut-off. Do not let low marks per question make you careless.

Habits that raise accuracy

• Read the question stem twice when it contains "not", "except", "incorrect" or "cannot be determined".
• In DI, write the unit next to your answer (₹ crore, thousand units, per cent) before matching options.
• In approximation questions, check the gap between options before you round. Close options need more care.
• In puzzles, draw every possible case, and answer only when a single case remains.
• In reading comprehension, find the line that supports your answer, not a line that "sounds like" it.
• Do not change answers at the end without a clear reason. Second thoughts under time pressure are often worse than first ones.

An accuracy log

After each mock, mark every attempted question as S (sure), T (two options left) or G (guess). Then fill in a log like this:

Three or four mocks of this tell you far more than any rule of thumb. Many candidates find their "sure" answers are right less often than they thought, which points to careless reading, not missing knowledge. Others find their two-option calls are right well over half the time, which means they can afford to attempt more of them.

Aim for 90% or more overall. If accuracy drops below about 80%, slow down before trying to attempt more.

Quick check

1. What is the penalty for a wrong answer in mains Reasoning? 0.375 (a quarter of 1.5).
2. A candidate has 40 correct and 8 wrong in the prelims. What is the net score? 40 − 2 = 38.
3. What is the expected value of a blind guess on a five-option question? Zero.
4. You can rule out two options on a DI question. What is the expected value of attempting? 2/6 ≈ +0.33 marks (m/6 with m = 2).
5. How many careless English errors cost the same as one careless DI error? Four: 4 × 0.625 = 2.5.
6. Does the descriptive paper have negative marking? No.

What to do next

• Add S, T and G marks to your next three mocks and fill in the accuracy log.
• Work out your net score, not just your attempts, after every sectional.
• Read the SBI PO prelims strategy for section-wise attempt plans.
• Use the mock test guide to build a proper analysis routine.