One of two biased coins A and B is selected and flipped 2 times. Let A be the event that coin A is selected and B be the event that coin B is selected, with probabilities p(A) = 0.4 and p(B) = 0.6. When coin A is flipped, the probability of heads is 0.9. When coin B is flipped, the probability of heads is 0.7. Let HHH be the event that the selected coin comes up heads 3 times. Required:
Find p(B|HHH).

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.