Question 1

Paper 1Easy7 marks

A fieldworker records the distance of seven sample plots from a road and the number of native plant species found in each plot.

Distance from road (m)51020355075100
Number of native plant species26811121413
(a)

Use a graphic display calculator to find Spearman’s rank correlation coefficient, rsr_s for these data. Give your answer to three significant figures.

[2]
(b)

Interpret your value of rsr_s in the context of the fieldwork.

[1]
(c)

The scatter plot suggests an overall increasing, curved relationship between distance from the road and the number of native plant species. State which coefficient, Pearson’s product moment correlation coefficient or Spearman’s rank correlation coefficient, is more appropriate for describing this relationship. Give a reason.

[2]
(d)

If one additional observation is an extreme value, explain how Pearson’s product moment correlation coefficient and Spearman’s rank correlation coefficient are likely to differ in their sensitivity to it.

[2]

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