An agricultural scientist conducted a controlled experiment to investigate the effect of a new organic foliar biostimulant spray on the daily growth rate of hydroponic pea shoots over a 10-day cultivation cycle. The trays of pea shoots in the experimental group were treated with the biostimulant spray once daily at 09:00 inside a ventilated greenhouse, while the trays in the control group were left untreated.
Identify one extraneous variable that could have affected the results of this study.
Suggest why it would have been important to control this extraneous variable and how the researcher could have controlled it.
Practise AQA A Level Psychology Scientific processes with exam-style questions for A Level Psychology. 689 questions, matched to the AQA A Level Psychology (7182) specification and written in Paper 1, Paper 2 and Paper 3 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.
