Question: 1. If the inspection division of a county weights and measures department wants to estimate the mean amount of soft-drink fill in 2-liter bottles to within ±0.01 liter with 95% confidence and also assumes that the standard deviation is ±0.05 liter, what sample size is needed?
2. A consumer group wants to estimate the mean electric bill for the month of July for single-family homes in a large city. Based on studies conducted in other cities, the standard deviation is assumed to be ±$25. The group wants to estimate the mean bill for July to within ±$5 with 99% confidence.
a. What sample size is needed?
b. If 95% confidence is desired, what sample size is necessary?