Correlation

Correlation(상관)

Linear relationship between two quantitative variables. Correlation variable r shows the direction and strength of the relationship.

-       Direction: Positive r means that if one variable increases, the other variable will increase too. Negative r means that if one variable increases, the other variable will decrease.

-       Strength: If the data points are all in one line, r is equal to ±1, and we call this ‘perfect linear relationship’. If there is no correlation between two variables, r is equal to 0.

We can calculate the correlation by this formula:

x bar: Average of group 1

y bar: Average of group 2

s: Standard deviation

 

You can’t compare the strength of relationship just by looking at the scatter plot. You must calculate it.