Question

A luxury car manufacturer keeps detailed records on all current owners of their vehicles. The marketing director takes a random sample of 9 customer records and finds an average age of 55 and a standard deviation of 6 for owners. Assuming all conditions of inference were met, what is the lower limit for a 95% confidence interval for the average age of all owners of this luxury car? (3 decimal places)

Answer 1

given data are:-

sample mean () = 55

sample sd (s) = 6

sample size (n) = 9

t critical value for 95% confidence level, both tailed test be:-

[ using t distribution table for df=(9-1) = 8,alpha=0.05,both tailed test]

the lower limit for a 95% confidence interval for the average age of all owners of this luxury car is:-

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