Source: Statistics at Square One (BMJ online)
How to access: This is free to access from the above link.
Contents: This is one chapter in Statistics at Square One (online). This section discusses how to calculate Person's correlation, how to make an inference (test, confidence interval), and Spearmans' rank correlation
Example(s) used in this: Hight and pulmonary anatomical dead space in 15 children
Prior math/stat knowledge to fully understand matrials: This is an introductory level and no prior statistical or mathematical knowledge would be required.