Spearman’s Rank
Biology: Cambridge International A Level, topic 18.1.5
Spearman’s Rank
Spearman's rank is a correlation test used to determine the significance of the relationship between datasets. You need a minimum of 10 data pairs to conduct this test. The steps involved are:
Null hypothesis
- State the null hypothesis.
- This is always that there is no significant relationship between dataset one and dataset two.
Calculation
- To calculate the Spearman's rank correlation coefficient using the below formula:
- \LARGE r_s = 1 - \frac {6 Σ D^2}{n({n^2}-1)}
- is the Spearman's rank correlation coefficient.
- is the difference between the results.
- is the no. of pairs.
Compare your value to critical value
- Look up the critical value for at the p = 0.05 significance interval.
- Compare your calculated value to the critical value.
- Reject the null hypothesis if your calculated value is equal to or greater than the critical value.
- This means there is a statistically significant relationship between the two datasets.
- Accept the null hypothesis if the calculated value is less than the critical value.
Test yourself on Spearman’s Rank
What is the minimum amount of pairs you need to conduct a Spearman's rank correlation test?
What significance level is used when conducting a Spearman's rank calculation?