Mastering Computer Based Tests (CBT) with Negative Marking: Accuracy vs Speed
Mahbubur Rahman (DU Math '19)
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4 min read
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18 Oct 2026
Negative marking penalizes guesswork. In StudyChamber's CBT testing engine, each correct answer awards +1.00 marks while an incorrect choice deducts 0.25 marks.
### The Math of Guessing
If you randomly guess 4 questions without elimination:
- 1 Correct = +1.00
- 3 Wrong = -0.75
- Net Gain = +0.25 (negligible, with high risk of -1.00).
### Two-Option Elimination Rule
Only attempt an uncertain question if you can definitively eliminate at least TWO options. With 50% odds, the mathematical expectancy becomes positive.
### The Math of Guessing
If you randomly guess 4 questions without elimination:
- 1 Correct = +1.00
- 3 Wrong = -0.75
- Net Gain = +0.25 (negligible, with high risk of -1.00).
### Two-Option Elimination Rule
Only attempt an uncertain question if you can definitively eliminate at least TWO options. With 50% odds, the mathematical expectancy becomes positive.
Mahbubur Rahman (DU Math '19)
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