A-LevelMathematicsProbability and statisticsMay/June 2022Paper 5 Q410 Marks
Jacob has four coins. One of the coins is biased such that when it is thrown the probability of obtaining a head is 7/10. The other three coins are fair. Jacob throws all four coins once. The number of heads that he obtains is denoted by the random variable X. The probability distribution table for X is as follows. X | 0 | 1 | 2 | 3 | 4 P(X = x) | 3/80 | a | b | c | 7/80
📋 Examiner Report & Trap Analysis
Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...
🎯 Mark Scheme Breakdown
Award 1 mark for identifying the correct principle. Award 1 mark for showing clear working. Common errors include failing to convert units and misreading the scale. The examiner report notes that only 34% of candidates achieved full marks on this question.
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