Environmental Science & Technology (Oct. 1993) reported on a study of contaminated soil in The Netherlands. A total of 72 400-gram soil specimens were sampled, dried, and analyzed for the contaminant cyanide. The cyanide concentration (milligrams per kilogram of soil) of each soil specimen was determined using an infrared microscopic method. The sample resulted in a mean cyanide level of y̅ = 84 mg/kg and a standard deviation of s = 80 mg/kg.

a. Test the hypothesis that the true mean cyanide level in soil in The Netherlands falls below 100 mg/kg. Use α = .10.

b. Would you reach the same conclusion in part a using α = .05? α = .01? Explain.