A-LevelMathematicsProbability and statistics9709/53 · May/June 2021 · Q24 Marks
The random variable X can take only the values -2, -1, 0, 1, 2. The probability distribution of X is given in the following table. [Table: X: -2, -1, 0, 1, 2; P(X = x): p, p, 0.1, q, q] Given that P(X > 0) = 3P(X < 0), find the values of p and q.
- Given that P(X > 0) = 3P(X < 0), find the values of p and q.[4]
Mark scheme
Marking points from the official mark scheme (May/June 2021). The mark or mark type is shown in brackets.
- [4] B1 Sum of probabilities = 1
- B1 Use given information
- M1 Either use of Substitution method to form a single equation in either p or q and finding values for both unknowns. Or use of Elimination method by writing both equations in same form (usually ap+bq = c ) and + or - to find an equation in one unknown and finding values for both unknowns.
- A1 CAO, both WWW
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