2 An investigation was conducted on patients aged less than 21 regarding who, if anyone, accompanied them to their appointment at a dental hospital (family member, a friend, attended alone). The fi ndings regarding the mean age for each group were:

With family member With friend Alone P- value 10.2 18.1 19.5 < 0.001

(i) State an appropriate null hypothesis about the mean age of the patients in the three groups.

(ii) Explain the statement “P < 0.001”.

(iii) What further testing could be performed between the three groups?

(iv) Why might the values of the means shown above cast doubt on the assumptions involved in applying one- way analysis of variance to these data?