A-LevelMathematicsProbability and statistics9709/61 · May/June 2019 · Q34 Marks
A fair six-sided die is thrown twice and the scores are noted. Event X is defined as 'The total of the two scores is 4'. Event Y is defined as ‘The first score is 2 or 5'. Are events X and Y independent? Justify your answer.
- (a)A fair six-sided die is thrown twice and the scores are noted. Event X is defined as 'The total of the two scores is 4'. Event Y is defined as ‘The first score is 2 or 5'. Are events X and Y independent? Justify your answer.[4]
Mark scheme
Marking points from the official mark scheme (May/June 2019). The mark or mark type is shown in brackets.
- [4] P(X) = 3 / 36 (1 / 12) oe. B1 P(Y) = 12 / 36 (1 / 3) oe. B1 P(X∩Y) = 1 / 36. Independent method to find P(X∩Y) without multiplication, either stated or by listing or circling numbers on a probability space diagram. OR conditional prob with a single fraction numerator M1 P(X) × P(Y) = P(X∩Y), independent. Numerical comparison and conclusion, www A1
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