A psychologist conducts a laboratory experiment to investigate the effects of sleep deprivation on cognitive performance. Which of the following scenarios represents a threat to the external validity of the study, rather than its internal validity?
The word-recollection task is extremely easy, leading to a ceiling effect where almost all participants score 100%.
The experimental group is tested in the morning while the control group is tested in the afternoon, introducing a confounding variable.
The sample consists entirely of elite military personnel trained to perform under sleep deprivation, limiting the generalisability of the findings.
Participants guess the purpose of the study from posters in the waiting room, changing their behaviour to match expectations.
644 exam-style questions on OCR A Level Psychology Research methods and techniques. Each one has a worked solution and a mark scheme showing where the marks go.