October 2021 Paper 2 Q8
8 The Normal variable \(X\) is transformed to the Normal variable \(Y\).
The transformation is \(y = a + bx\), where \(a\) and \(b\) are positive constants.
You are given that \(X \sim N(42, 6.8)\) and \(Y \sim N(57.2, 11.492)\).
Determine the values of \(a\) and \(b\). [4]
| Scheme | Marks | AO |
|---|---|---|
| \(b^2 = \dfrac{11.492}{6.8}\) oe | M1 | 3.1a |
| \(b = 1.3\) | A1 | 1.1 |
| \(42b + a = 57.2\) | M1 | 1.1 |
| \(a = 2.6\) | A1 | 3.2a |
| [4] |
Notes
M1: \(b\) may be incorrect numerical value