In Exercise 2.85 (page 77), we briefly described a series of international quality standards called ISO 9000. In the results of a Quality Systems Update/Deloittc & Touche survey of ISO 9000 registered companies published by CEEM Information Systems, 515 of 620 companies surveyed reported that they are encouraging their suppliers to pursue ISO 9000 registration.8
a. Using these survey results, compute a 95.44 percent confidence interval for the proportion of all ISO 9000 registered companies that encourage their suppliers to pursue ISO 9000 registration. Assume here that the survey participants have been randomly selected.
b. Based on this interval, is there conclusive evidence that more than 75 percent of all ISO 9000 registered companies encourage their suppliers to pursue ISO 9000 registration?