To quantify the strength and direction of the relationship between two variables, we use the linear correlation coefficient: Linear Correlation Coefficientīecause visual examinations are largely subjective, we need a more precise and objective measure to define the correlation between the two variables.
When one variable changes, it does not influence the other variable. When two variables have no relationship, there is no straight-line relationship or non-linear relationship. For example, as age increases height increases up to a point then levels off after reaching a maximum height. Non-linear relationships have an apparent pattern, just not linear. Scatterplot of temperature versus wind speed. For example, as wind speed increases, wind chill temperature decreases. Negative relationships have points that decline downward to the right. For example, when studying plants, height typically increases as diameter increases. Positive relationships have points that incline upwards to the right. Linear relationships can be either positive or negative. This is the relationship that we will examine. A relationship is linear when the points on a scatterplot follow a somewhat straight line pattern.