Q312 · Practice questionTechnology-freeSimple familiar3 marks
QUESTION 312 (3 marks)
A council wants to estimate the proportion of residents who support a new skate park. It surveys every fifth person entering the existing skate park between pm and pm on Saturday.
a)[1 mark]
Explain one source of sampling bias.
b)[2 marks]
Describe a practical random sampling procedure that better represents all residents.
WORKED SOLUTION
3 marksPractice marking scheme
ANSWER
a) Current skate-park visitors may be more supportive than residents generally. b) Randomly select residents from a complete resident sampling frame and contact those selected, making reasonable follow-up attempts.
Worked solution
a) The location restricts the sample to a group likely to have a particular interest in skate facilities. Time restrictions may further change the mix of respondents.
b) Use a frame covering the target population, assign identifiers and use random numbers to select residents. Contact the selected residents, with follow-up to reduce nonresponse.
Exact answers unless rounding is specified; equivalent forms accepted.
a) Identifies a bias and links it to the target population.
b) Uses a frame covering all residents.
b) Specifies a genuine random selection method.
Practice question aligned to the current QCAA syllabus; review the worked solution and marking criteria.
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