3. a. The average zinc concentration recovered from a sample of measurements taken in 25 different locations in a river is found to be 1.6 grams per milliliter. Find the 95% and 99% condence intervals for the mean zinc concentration in the river, Assume that the population standard deviation is 0.2 gram per milliliter. h. HW large a sample is required if we want to be 95% condent that our estimate of p in (a) is offby less than BIB? [Pagci 4. In a random sample of n = 400 families owning television sets in the citsr of Hamilton, Canada, it is found that x = 24E! subscribe to H130. Find a 99% condence interval for the actual proportion of families with television sets in this city that subscribe to HBO