A coal-fired power plant is considering two different systems for pollution abatement. The first system has reduced the emission of pollutants to acceptable levels 68% of the time, as determined from 200 air samples. The second, more expensive system has reduced the emission of pollutants to acceptable levels 70% of the time, as determined from 250 air samples. lf the expen sive system is significantly more eilective than the inexpensive system in reducing the pollutants to acceptable levels, then the management of the power plant will install the expensive system.