Numerical variable: relationship

Learning objectives

  • Make a scatterplot to display the relationship between two quantitative variables.
    • Look at the direction, form, and strength of the relationship, and any outliers that stand away from the overall pattern.
  • Provided the form of the relationship is straight, summarize its strength with a correlation, r.
    • The sign of the correlation gives the direction of the relationship.
    • -1 <= r <= 1 ; A correlation of 1 or -1 is a perfect linear relationship. A correlation of 0 indicates that there is no linear relationship.
    • Correlation has no units, so shifting or scaling the data, standardizing, or even swap- ping the variables has no effect on the numerical value.
  • A large correlation is not a sign of a causal relationship.

Checklist

  • Finish reading: Correlation (You can safely ignore any formulas about the correlation score, and everything in the Kendall’s Tau and Spearman’s Rho part.)

Optional