6. A survey found that of the 320 people questioned who had passed their driving test aged under twenty-five, 104 had been involved in an accident in the two years following their test. Of the 80 people in the survey who were aged twenty-five or over when they passed their test, 16 had been involved in an accident in the following two years.

1. Draw up a contingency table showing this information. It is desired to test whether the proportion of drivers having accidents within two years of passing their test is different for those who were aged under twenty-five at the time of passing their test than for those aged twenty-five or over.
2. 1. Stating your hypotheses clearly, carry out the test at the \(5 \%\) level of significance.
   2. Explain clearly why there is only one degree of freedom. It is found that 12 people who were aged under twenty-five when they took their test and had been involved in an accident in the following two years had been omitted from the information given.
3. Explain why you do not need to repeat the calculation to know the correct result of the test.
   (2 marks)