Correlation quantifies the extent to which two quantitative variables, X and Y, “go together.” When high values of X are associated with high values of Y, a positive correlation exists.

A correlation matrix is a useful way to summarize a set of correlations and is more commonly used as the number of correlations conducted increases. From a correlation matrix we can …

Recall when we introduced scatter plots in Chapter 1, we assessed the strength of the association between two variables by eyeballs. Correlation r is a numerical measure of the direction and …

A correlation simply looks at the strength and direction of a relationship For example, a study found that ice cream sales was strongly positively correlated with shark attacks.

The correlation coefficient simply describes the degree of relationship between two variables } A correlation does not tell us why two variables are related, nor does it allow for causal …

A correlation is a single number that describes the degree of relationship between two variables. Scatter plot of two variables will visualize the relationship among them.

The correlation coefficient r (also known as Pearson’s r) is a number that tells us the strength of the relationship between the independent variable x and dependent variable y.