(a) A TV news bulletin asked viewers to phone in their response to the question: “Should asylum seekers who break out of detention be penalised for doing so?” Respondents dialled different numbers to register “yes” or “no” answers.
(i) Identify at least two sources of bias in this survey.
(ii) Why would it be wrong for the TV station to interpret the results of the survey as an indication of “public opinion”?
(b) Giving brief reasons in each case, indicate whether MAS183 students are likely to be representative of Murdoch University students in relation to –
(i) attitudes to public policy on climate change; and
(ii) brand of mobile phone.
Coverage bias: A telephone survey suffer from coverage bias because it cannot include viewers without telephones.
Voluntary response bias: Voluntary response bias occurs when sample members are self-selected volunteers. The persons who have a strong opinion (who feel strongly that they should answer the question) is likely to call. The resulting sample tends to overrepresent individuals who have strong opinions.
(ii) Apart from the biases stated above, the resulting opinion can not be taken as "public opinion" since the number of people who call there is a very small part of the total population.
(b)-- Try yourself.