20.26 Body Mass Index of Young Men. In Example 16.1 (page 368), we developed a 95% z confidence interval for the mean body mass index (BMI) of American men aged 20-29 years, based on a national random sample of 936 such men. We assumed there that the population standard deviation was known to be o-11.6. In fact, the sample data had mean BMI x -27.2 and standard deviation s=11.63. What is the 95% t confidence interval for the mean BMI of all American young men