the pesticide diazinon is in common use to treat infestations of the german cockroach, blattella germanica. a study investigated the persistence of this pesticide on various types of surfaces. researchers applied a 0.5% emulsion of diazinon to glass and to plasterboard. after 14 days, they randomly assigned 90 cockroaches to two groups of 45, placed one group on each surface, and recorded the number that died within 48 hours. on glass, 21 cockroaches died, while on plasterboard 30 died. we wish to determine if this is convincing evidence that the proportion of all cockroaches which will die when exposed to diazinon on plasterboard, pp, is greater than the proportion of all cockroaches which will die when exposed to diazinon on glass, pg.