Negative Marking Under a Mismatched Clock
You are 62 minutes into a 90-minute computer-based entrance test of 120 single-best-answer questions. Scoring is +4 for a correct answer, −1 for a wrong answer, and 0 for a blank. You have answered 70 questions, flagged 12, and estimate that 8 of the flagged are probably correct. The remaining 50 questions feel harder than the first half. At question 78, a 50 kg patient dose calculation gives you 0.45 mg/kg. The four options are 18 mg, 22.5 mg, 27 mg, and 31.5 mg. You are confident the answer is either 22.5 mg or 27 mg but cannot recheck because the on-screen calculator is disabled and your rough paper is nearly full. The centre clock reads 28 minutes left, but your wristwatch, which you set at the start, reads 31 minutes. Invigilators have announced no extra time. You still have 12 flagged questions and 42 unseen questions.
1. Should you answer question 78 now, leave it blank, or flag it and return? Show the expected-value reasoning and state what you would do about the clock discrepancy.
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Answer it now. The expected value of a guess between two equally plausible options is (0.5 × +4) + (0.5 × −1) = +1.5 marks, which is better than leaving it blank. Flagging and returning would only make sense if you had a real method to resolve the uncertainty, but you have no calculator and little rough paper; the 22.5 mg value follows directly from 50 × 0.45, so choose 22.5 mg and move on. The clock discrepancy changes the budget, not the answer. Treat the centre clock as authoritative: 28 minutes, not 31. Trying to resolve the discrepancy during the test wastes time and raises anxiety. Note the question number, the two clock readings, and the time you noticed the mismatch, then report it in writing to the exam coordinator after the test. Do not let the issue become a reason to rush the remaining items.
2. With 28 minutes for 54 remaining questions, propose a time budget and a rule for when to skip a question. Include how you would handle the 12 flagged items.
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The raw average is about 31 seconds per question, but flagged items are not all unseen. Allocate roughly 20 minutes to the 42 unseen questions, about 28 seconds each, and 8 minutes to the 12 flagged questions, about 40 seconds each. Use a hard skip rule: if an unseen question has no clear path after 45 seconds, mark a guess only if you can eliminate at least one option; otherwise leave it blank and return only if time remains. Under +4/−1, the break-even probability is 20%, so a blind four-option guess is slightly positive in expected value, but time has an opportunity cost. For the flagged items, do not reopen all 12. You estimate 8 are probably correct; revisit only those where you remember a specific doubt or a unit error. Changing a first answer without a concrete reason tends to reduce accuracy. Keep 2 minutes as a final check for misgridded or blank items.
3. The invigilator says the centre clock is authoritative and cannot be corrected. How should that affect your last 28 minutes, and what would you do after the test?
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Accept the 28-minute figure immediately and recompute the plan without argument. The practical effect is to cut about 3 minutes from the original budget: reduce the unseen-question allowance from 22 to 20 minutes and the flagged review from 10 to 8 minutes. Do not spend even 60 seconds debating the clock with the invigilator; that is time you cannot recover. After the test, write a short factual note to the exam coordinator: centre name, candidate number, the question you were on when you noticed the mismatch, the centre clock reading, your wristwatch reading, and the invigilator's statement. Ask whether any time adjustment or incident report is possible. Keep the tone neutral and avoid alleging misconduct. The goal is to create a record without turning a 3-minute discrepancy into a bigger distraction.