Exercise 4 Each tennis court contains a confidence interval for the true population mean resonance frequency (Hz) for all tennis rackets of a certain type. Both confidence intervals use the same sample mean, sample standard deviation, and sample size; the only difference between them is the confidence level. (a) What is the value of the sample mean resonance frequency x used to construct both confidence intervals? (b) Both intervals were calculated from the same sample data, but the confidence level for one of these intervals is 90% and the other is 99%. Which interval, [114.4, 115.6] or [114.1, 115.9], has a confidence level of 90%? Why?

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