An ecologist is studying the effect of soil salinity, s s\,s mS/cm, on the maximum growth height, h h\,h cm, of a marsh grass. She records s s\,s and h h\,h at each of 10 sites and plots the data on a scatter diagram.
For 9 of the sites the points show a strong negative linear correlation, and the product moment correlation coefficient for those 9 sites is -0.824.
The 10th site, Site Omega, is plotted at (48, 82)(48,\ 82)(48, 82), which lies well above the trend shown by the other 9 sites.
State why Site Omega might be considered an outlier in this context.
State, giving a reason, what effect including Site Omega would have on the value of the product moment correlation coefficient.
The ecologist decides to delete Site Omega before fitting a model. Give one argument in favour of deleting it and one argument against.
244 exam-style questions on AQA A Level Maths 2.2 L: Data presentation and interpretation, covering 2.2.1 Single-variable data diagrams, 2.2.2 Scatter diagrams and correlation, 2.2.3 Central tendency, variation and standard deviation, 2.2.4 Outliers and cleaning data, and 2.2 L: Data presentation and interpretation. Each one has a worked solution and a mark scheme showing where the marks go.