A mobile phone dealer sold a total of 74 mobile phones in july and 8 less than that in august. In september the sale is even 5less than in august. If the number of mobile phones sold in the three months were combined, how many mobile phones were sold in all?

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.