Table 6.11 Description of Variables for Boston Housing Example CRIM Per capita crime rate by town ZN Proportion of residential land zoned for lots over 25,000 ft INDUS Proportion of nonretail business acres per town CHAS Charles River dummy variable (=1 if tract bounds river; =0 otherwise) NOX Nitric oxide concentration (parts per 10 million) RM Average number of rooms per dwelling AGE Proportion of owneroccupied units built prior to 1940 DIS Weighted distances to five Boston employment centers RAD Index of accessibility to radial highways TAX Full-value property-tax rate per $10,000 PTRATIO Pupil/teacher rato by town LSTAT Percentage lower status of the population MEDV Median value of owneroccupied homes in $1000s