A study was conducted at the University of Waterloo on impact characteristics of football helmets employed in competitive high school programs. There were three kinds of helmets considered, classified according to the liner type: suspension, padded-suspension, and padded. In the study, a measurement called Gadd Severity Index (GSI) was obtained on each helmet using standardized impact test. A helmet was deemed to have failed if the GSI was greater than 1200. Of 81 helmets tested, 29 failed GSI 1200 criterion.
Based upon the sample results, determine the 90% confidence interval estimate for the true population proportion of suspension helmets that would fail the test?