Porsche Cars North America keeps detailed records on all current Porsche owners. The marketing director takes a random sample of 9 customer records and finds that the average age of a Porsche owner is 52.8 years with a standard deviation of 6.1 years. Assuming all conditions of inference were met, what is a 95% confidence interval estimate for the average age of all Porsche owners? 6.1 (A) 52.8 ± 2.306 x 3 6.1 (B) 52.8 ± 2.306 × (C) 52.8±2.262 x (D) 52.8±2.262 x 6.1 3 6.1 6.1 (E) 52.8±1.96 x 3

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