data(xs.nz)xs.nz[, 12] are dangerous.
Also, variable names may change in the future as well as
their format or internal structure,
e.g., factor versus numeric.Although some data cleaning was performed and logic checks conducted, anomalies remain. Some variables, of course, are subject to a lot of measurement error and bias. It is conceivable that some participants had poor reading skills!
chest.nz.