A council library gives a psychologist access to its borrowing records. For each adult volunteer, the psychologist records the number of books borrowed during the previous year and obtains a score from a 40-item vocabulary test. An assistant labels the borrowing total as the IV and the vocabulary score as the DV.
Explain why these labels do not match the way the psychologist collected the data and why the two scores should be treated as co-variables. Identify one extraneous variable that could account for an association between the scores.
139 exam-style questions on OCR GCSE Psychology 7.2 Doing Research, covering 7.2.1 Experiments, 7.2.2 Interviews, 7.2.3 Questionnaires (Surveys), 7.2.4 Observations, 7.2.5 Case Studies, and 7.2.6 Correlations. Each one has a worked solution and a mark scheme showing where the marks go.