An ecologist was interested in the relationship between soil moisture levels and the growth of Vaccinium myrtillus (bilberry) shrubs in a large national park. She decided to investigate whether or not a relationship existed across the entire park.
The ecologist designed a measurement protocol to assess the average height of the shrubs. She selected a single 10 m×10 m10\text{ m} \times 10\text{ m}10 m×10 m quadrat located near the main research station's access road. Thirty bilberry shrubs within this single quadrat were selected and their heights measured.
To measure soil moisture, she placed three tensiometers at fixed points within this same quadrat. Readings (in centibars) were recorded daily at noon over a two-week period during mid-summer. Using these measurements, she calculated a single average soil moisture level for the quadrat.
Question Apart from the issue of validity, identify and briefly explain one methodological limitation of the study.
689 exam-style questions on AQA A Level Psychology Scientific processes. Each one has a worked solution and a mark scheme showing where the marks go.