Background data: Bates doesn't know if "half" is correct. He looked through his records, and found that of the most recent 150 guest visits at the motel, the shower curtain has been ripped and required replacement 85 times.

Question h: Obtain a 90% confidence interval for the true proportion of guest visits that result in a ripped shower curtain.

Please answer the question using excel. Please show the excel formulas and calculations used to solve the question.