RBI Assistant – Foundation & Exam Strategy
Topic: Marking Scheme
Why this section matters
The marking scheme is the backbone of every RBI Assistant test.
Understanding how marks are awarded and penalised lets you:
- estimate the expected score for a given accuracy level
- decide whether to attempt a question or skip
- optimise your time‑management strategy
- avoid costly mistakes that can turn a good answer into a loss
1. Core Rules (as per the latest RBI Assistant notification)
| Section | Number of Questions | Marks per Correct | Marks per Wrong | Marks for Unattempted |
|---|---|---|---|---|
| General Knowledge | 25 | +1 | –0.25 | 0 |
| Quantitative Aptitude | 25 | +1 | –0.25 | 0 |
| Reasoning | 25 | +1 | –0.25 | 0 |
| English | 25 | +1 | –0.25 | 0 |
| Total | 100 |
Key take‑away – Every question carries the same weight.
No partial credit; no negative marks for leaving a question blank.
2. The Math Behind the Score
Let
- (C) = number of correct answers
- (I) = number of incorrect answers
- (U) = number of unattempted questions
We always have
[
C + I + U = 100 \quad\text{(total questions)}
]
2.1 Raw Score Formula
[ \boxed{\text{Score} = 1 \times C - 0.25 \times I} ]
2.2 Expressing Score in Terms of Accuracy
If you know your accuracy (A = \frac{C}{100}) and decide to attempt (T) questions (so (T = C+I)), the score can be written as:
[ \text{Score} = 1 \times C - 0.25 \times (T-C) = 1.25C - 0.25T ]
Since (T = 100-U),
[ \text{Score} = 1.25C + 0.25U - 25 ]
Why this matters
- If you know you will answer (T) questions, you can compute the minimum and maximum possible score quickly.
- It also shows that skipping (increasing (U)) actually raises the base “floor” by (0.25) per skipped question, but you lose the chance to score +1 on a correct answer.
2.3 Extreme Scenarios
| Scenario | (C) | (I) | (U) | Score |
|---|---|---|---|---|
| All correct | 100 | 0 | 0 | 100 |
| All wrong | 0 | 100 | 0 | –25 |
| All skipped | 0 | 0 | 100 | 0 |
The lowest possible score is –25, but it is rarely advantageous to attempt every question.
3. Strategic Implications
| Decision | Expected Score (assuming accuracy (p)) | When to Do It |
|---|---|---|
| Answer all | (100p - 25(1-p)) | If (p > 0.2) (i.e., >20 % correct) you’ll get a positive score. |
| Skip after 1/4 of questions | (0.75 \times ( \frac{C}{0.75} - 0.25 \times \frac{I}{0.75})) | If you’re uncertain after 25–30 s per question (or if (p < 0.2)) |
| Skip a single question | +0.25 (since you avoid the chance of losing 0.25) | When you’re truly unsure (time‑pressure + low confidence). |
3.1 “Risk‑Reward” Decision
The break‑even accuracy level when you attempt a question is:
[ \text{Expected Gain} = p \times 1 - (1-p) \times 0.25 = 0 ] [ p - 0.25 + 0.25p = 0 \quad\Rightarrow\quad 1.25p = 0.25 \quad\Rightarrow\quad p = 0.20 ]
If you are confident of >20 % correctness on a question, answer it; otherwise, skip.
3.2 Time Management Hint
- Spend ~30 s on a difficult question.
- If you