a sample of checks written by a company is examined for propriety. for each canceled check there was a voucher jacket included with supporting documents. according to company policy, the number of checks without supporting documentation should be minimized. an auditor wants to estimate the proportion of checks without supporting documentation. what sample size would be needed to obtain a 90% confidence interval on the proportion of checks without documentation that has a margin of error of .03? assume that a preliminary sample of size 150 was taken and that 20 were found not to have documentation.