- The random variable \(X\) has an \(F\) distribution with 10 and 12 degrees of freedom. Find \(a\) and \(b\) such that \(\mathrm { P } ( a < X < b ) = 0.90\).
(3) - A chemist has developed a fuel additive and claims that it reduces the fuel consumption of cars. To test this claim, 8 randomly selected cars were each filled with 20 litres of fuel and driven around a race circuit. Each car was tested twice, once with the additive and once without. The distances, in miles, that each car travelled before running out of fuel are given in the table below.
| Car | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| Distance without additive | 163 | 172 | 195 | 170 | 183 | 185 | 161 | 176 |
| Distance with additive | 168 | 185 | 187 | 172 | 180 | 189 | 172 | 175 |
Assuming that the distances travelled follow a normal distribution and stating your hypotheses clearly test, at the \(10 \%\) level of significance, whether or not there is evidence to support the chemist's claim.
(8)