Monday, 20 May 2013

Fieldwork: Spearman's Rank Correlation Coefficient

A simple statistical test examining the relationship between 2 sets of data.

95% significance: 0.377       99% significance: 0.534

For % of vegetation cover: +0.41 so there is a 95% certainty that it and distance from the sea are related.

For number of plant species: +0.47 so there is a 95% certainty but is more than vegetation cover

There is a moderate positive correlation.

Given that we had had 20 sites we can say with certainty that there is a 95% correlation between the variables. We can't be 99% sure.


  • Tells whether direction of relationship is positive or negative
  • Tells exactly the strength of the relationship unlike the scattergraph which only gives a general indication


  • Correlation does not equal causation
  • Simplistic technique
  • Need at least 10 sets of data

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