Mr Hughes tests whether revising with a highlighter improves recall of a short passage. He reads the instructions aloud to each participant. For the highlighter condition he reads them warmly and adds, "This usually helps a lot." For the no-highlighter condition he reads them in a flat voice with no comment.
Explain one way this procedure could reduce the validity of Mr Hughes's findings.
182 exam-style questions on OCR GCSE Psychology 7.1 Planning Research, covering 7.1.1 Hypotheses, 7.1.2 Variables, 7.1.3 Experimental Designs, 7.1.4 Populations and Sampling, 7.1.5 Ethical issues, and 7.1.6 Dealing with ethical issues and BPS Code. Each one has a worked solution and a mark scheme showing where the marks go.