Which BEST explains the expression w( xy z − 5 2 )? A) w depends on ( xy z − 5 2 ). B) ( xy z − 5 2 ) depends on w. C) w and ( xy z − 5 2 ) are dependent on each other. D) w and ( xy z − 5 2 ) are independent of each other.

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.