It is claimed that a certain low fat ice cream bars contains average saturated fat content of 0.5 gram. In a random sample of 12 bars of this brand the sample average saturated fat is 4.72 grams with sample standard deviation of 0.0648 grams. Assuming normal distribusion for the fat content:
a) what it the probability that the average saturated fat content is within 4,8 and 5.2 gram?
b) what is the maximum standard deviation of saturated fat content with 95% confidence?
c) what sample size is needed to reduce the error of estimation in part a above by half (reduce it by 50%)