An environmental engineer is investigating whether a new bio-filtration system reduces the concentration of nitrates in runoff water compared to a standard sand-filter system. They set up 24 test plots, randomly assigning 12 to use the bio-filtration system and 12 to use the standard sand-filter system. After a simulated rainfall event, they measure the nitrate concentration in the runoff from each plot in parts per million (ppm).
Suggest an appropriate statistical test the engineer could use to analyse the data. Justify your choice of test.
121 exam-style questions on AQA A Level Psychology Inferential testing (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.