Suppose the Allmans want to rent a convertible for the day. They have a choice of two rental companies: A one-day rental at Nifty Car Rental costs $30 plus 60 cents per mile.
A one-day rental at Shazam Car Rental costs $55 but only charges 35 cents per mile.

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.