Question

What statistical test would I use if I were to test the correlation between 3 variables?

Example:

Let's say I wanted to know how county human population abundance impacts the amount of plastics found in sediment & and the amount of plastics found in oysters

Answer 1

Multiple Correlation is used when there are more than 2 variables.

The coefficient of multiple linear correlation is R (with necessary subscript)

Let say

Dependent variable is X_{​​​​​​1}

Independent variables are X_{​​​​​​2} , X_{​​​​​​3}

So R_{​​​​​​1.23} is the multiple correlation coefficient with X_{​​​​​​1} as the dependent variable and X_{​​​​​​2}  , X_{​​​​​​3}as the independent variables.

R_{​​​​​​1.23} =

As,

And r_{​​​​​​12}  (or r_{​​​​​​13} ) is the simple correlation between variable 1 and 2 (or 1 and 3).