1. consider a normal population distribution with the value of s known. a. what is the confidence level for the interval ? b. what is the confidence level for the interval ? c. what value of in the ci formula (7.5) results in a confidence level of 99.7%? d. answer the question posed in part (c) for a confidence level of 75%. 2. each of the following is a confidence interval for m true average (i. e., population mean) resonance frequency (hz) for all tennis rackets of a certain type: (114.4, 115.6) (114.1, 115.9) a. what is the value of the sample mean resonance frequency? b. both intervals were calculated from the same sample data. the confidence level for one of these intervals is 90% and for the other is 99%. which of the intervals has the 90% confidence level, and why? za/2 1.44s/ 1n x 6 2.81s/ 1n x 6