A marine biologist conducted an environmental survey to investigate whether the presence of microplastics in shore crabs (Carcinus maenas) differs depending on the estuary from which they were sampled. Over a two-week period, the biologist collected crabs from two distinct locations: Estuary A (near an industrial zone) and Estuary B (near a nature reserve). They recorded whether microplastics were detected or not detected in the digestive tract of each crab. The results are shown in the table below.
Table showing the number of crabs with microplastics detected or not detected across two estuaries
| Microplastic Presence | Estuary A | Estuary B |
|---|---|---|
| Detected | 24 | 11 |
| Not detected | 8 | 21 |
The biologist used a Chi-square test of association to analyse the data.
Give one reason why the Chi-square test is the appropriate statistical test to use for this study.
513 exam-style questions on OCR A Level Psychology Data recording, analysis and presentation. Each one has a worked solution and a mark scheme showing where the marks go.