The Mining data set contains the results of an experiment to determine whether drilling time was faster for wet drilling or dry drilling (Penner and Watts; 1991). Tests were replicated three times for each method at different test holes. There is one observation per five-foot interval for each replication.
The following list describes each variable.
depth of the hole, in feet
time to drill the last five feet of the current depth, in minutes
drilling method, wet or dry
replicate number