1MA0 Higher June 2014 Paper 2 Q22
*22 Shabeen has a biased coin.
The probability that the coin will land on heads is 0.6
Shabeen is going to throw the coin 3 times.
She says the probability that the coin will land on tails 3 times is less than 0.1
Is Shabeen correct?
You must show all your working. (3)
| Answer | Mark | Notes |
|---|---|---|
| Yes | 3 | M1 for \(1 - 0.6\) (=0.4) M1 for \((\text{``}0.4\text{''})^3\) oe C1 (dep on M1) for 0.064 oe leading to a correct deduction OR M1 for \(1 - \text{Pr}(3\text{H}, 0\text{T}) - \text{Pr}(2\text{H}, 1\text{T}) - \text{Pr}(1\text{H}, 2\text{T})\) oe M1 for \(1 - (0.6)^3 - 3(0.6)^2(0.4) - 3(0.6)(0.4)^2\) C1 (dep on M1) for 0.064 oe leading to a correct deduction |