z score for One research study of illegal drug use among 12- to 17-year-olds reported a decrease in use (from 11.4% in 1997) to 9.8% now. Suppose a survey in a large high school reveals that, in a random sample of 1,050 students, 99 report using illegal drugs. Use a 0.05 significance level to test the principal's claim that illegal drug use in her school is below the current national average.