A psychologist tests whether a brief goal-setting exercise increases persistence on difficult puzzles. She expects the exercise to work. She smiles and gives extra encouragement when instructing participants who completed the exercise, but uses a neutral tone with the comparison group.
A separate observer watches recordings to decide whether pauses count as "still trying". The recordings are labelled with each participant's group, and the observer knows the psychologist's hypothesis.
The psychologist concludes that the goal-setting exercise increases persistence.
Identify two different sources of bias in this study. Explain how each source of bias could make the conclusion appear better supported than it is.
173 exam-style questions on OCR GCSE Psychology 7.3 Analysing Research, covering 7.3.1 Types of Data, 7.3.2 Measures of central tendency, 7.3.3 Other descriptive statistics, 7.3.4 Tables, Charts and Graphs, 7.3.5 Reliability, 7.3.6 Validity and effects on validity, and 7.3.7 Sources of bias. Each one has a worked solution and a mark scheme showing where the marks go.