17.5 In a poll about changes to pension entitlements a random sample of 160 workers were asked if they would prefer to retire at 65 years of age or work beyond 65. Their responses, and the nature of their work is summarised in the following contingency table:

Nature of work Retire at 65 Work beyond 65 Professional/managerial 12 18 Administrative/clerical 47 33 Craft/manual 34 16 Test the null hypothesis of no association between retirement preference and nature of work department using (i) a 5% level of signifi cance, and (ii) a 1% level of signifi cance.