In Canada, the vast majority (90%) of companies in the chemical industry are ISO 14001 certified. The ISO 14001 is an international standard for environmental management systems. An environ-mental group wished to estimate the percentage of U.S. chemical companies that are ISO 14001 certified. Of the 550 chemical companies sampled, 385 are certified.
a) What proportion of the sample reported being certified?
b) Create a 95% confidence interval for the proportion of U.S. chemical companies with ISO 14001 certification. (Be sure to check conditions.) Compare to the Canadian proportion.