Ling wants to determine the average distance she travels each day in her car. she records the odometer reading each morning for a week. day 1 2 3 4 5 6 7 odometer (mi) 10,150 10,211 10,424 10,769 10,884 11,155 11,477 what is the mean distance ling travels each day? show your work

Arandom sample of n = 25 observations is taken from a n(µ, σ ) population. a 95% confidence interval for µ was calculated to be (42.16, 57.84). the researcher feels that this interval is too wide. you want to reduce the interval to a width at most 12 units. a) for a confidence level of 95%, calculate the smallest sample size needed. b) for a sample size fixed at n = 25, calculate the largest confidence level 100(1 − α)% needed.