17.5 Logging in the rain forest. "Conservationists have despaired over destruction of trop ical rain forest by logging, clearing, and burning." These words begin a report on a statistical study of the effects of logging in Borneo.'' Here are data on the number of tree species in 12 unlogged forest plots and 9 similar plots logged 8 years earlier:
Unlogged 22 18 22 20 15 21 13 13 19 13 19 15 Logged 17 4 18 14 18 15 15 10 12

(a) The study report says, "Loggers were unaware that the effects of logging would be assessed." Why is this important? The report also explains why the plots can be considered to he randomly assigned.

(b) Does logging significantly reduce the mean number of species in a plot after 8 years?
Follow the four-step process as illustrated in Examples 17.3 and 17.4.