I don't get how to do these two inter-related problems. I have the answer to the first one, but not the second. The questions are:
1. A random sample of 4 Herefords, each with a frame size of three (on a one-to-seven scale), gave a sample mean weight of 452 kg. The known population standarad deviation is 12 kg. A 95% confidence interval for the average weight of all Herefords of this frame size is (using an "exact" confidence interval):
The answer is (432.9, 471.1), but I was getting (440.2, 463.8). How do you get the right answer?
2. Referring to the previous question, about how many animals should be sampled (in total) in order to be 95% confident of determining the true mean weight WITHIN 2 kg?
The answer is either 138, 139, 140, 550, or 190. Keep in mind if you get a non-whole answer (which you will), you must round up, no matter what.
Thanks for your help.