A psychologist conducts an investigation to compare the effectiveness of a 'Virtual Reality (VR) mindfulness session' versus 'outdoor forest-bathing (Shinrin-yoku)' on the stress levels of corporate employees. Stress is measured using salivary cortisol levels (in μg/dL\mu\text{g/dL}μg/dL) after a 30-minute intervention.
State a suitable null hypothesis for this investigation.
638 exam-style questions on Edexcel A Level Psychology Methods. Each one has a worked solution and a mark scheme showing where the marks go.