Refer to the CSI Computer Crime and Security Survey, first presented in Exercise 1.19. Recall that of the 351 organizations that responded to the survey, 144 (or 41%) admitted unauthorized use of computer systems at their firms during the year. Estimate the probability of unauthorized use of computer systems at an organization with a 90% confidence interval. Explain how 90% is used as a measure of reliability for the confidence interval.

Data from Exercise 1.19

The Computer Security Institute (CSI) conducts an annual survey of computer crime at United States businesses. CSI sends survey questionnaires to computer security personnel at all U.S. corporations and government agencies. The 2010 CSI survey as sent by post or email to 5,412 firms and 351 organizations responded. Forty-one percent of the respondents admitted unauthorized use of computer systems at their firms during the year. (CSI Computer Crime and Security Survey, 2010/2011.)