This gives the degree of pneumoconiosis (normal, present, or severe) in a group of coalminers as a function of the number of years worked at the coalface. The degree of the disease was assessed radiologically and is qualitative.
Pneu
A data frame with 8 observations on the following 4 variables
Years
Period of exposure (years worked at the coalface)
Normal
Number of miners with normal lungs
Present
Number of miners with disease present
Severe
Number of miners with severe disease
Davison, A. C. (2003) Statistical Models. Cambridge University Press. Page 509.