An ecologist investigates soil salinity and the maximum height of marsh grass at 10 sites. Nine points follow a strong negative linear pattern. The tenth point lies well above this pattern. Software gives r=−0.92r=-0.92r=−0.92 for the nine points and r=−0.61r=-0.61r=−0.61 when the tenth point is included.
Explain why the tenth point may be described as an outlier in this context.
Describe and explain its effect on the sample product moment correlation coefficient.
Explain why the ecologist should investigate the point before deciding whether to remove it.
308 exam-style questions on WJEC A Level Maths 4.3 Statistical hypothesis testing (A-level only), covering 4.3.1 Statistical hypothesis testing (A-level only) and 4.3.2 Statistical hypothesis testing (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.