5.2 What types of relationship might exist between two quantitative variables?
5.2.2 Statistical relationship
This is measured according to how well an explanatory (predictor) variable can explain the variability in a response variable. The statistical tools used in investigating such a relationship include:
a scatterplot graph of the bivariate data - just as we drew graphs of univariate data - this is a most important starting point;
the regression line (least squares line) which indicates the trend of the data - much like the measures of central tendency for univariate data (mean and median) indicate the centre of a univariate data set;
correlation (co-relation) - which measures the strength of the association by the closeness of the data points to the regression line - just as the standard deviation described how far away the data points of a univariate data set are from the mean.
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