A machine fills bags with content. From the production a sample takes out and each bag is weighed.

In Table 1 is the result from the measurements. From previous experiences you know that the

weights follow a normal distribution.

Table 1: The weight on the bags in gram

100.7 95.9 103.8 101.2 100.5

102.1 101.0 96.2 99.4 99.4

a) Calculate a 95% confidence interval for the mean weight on the bags. What conclusions can one make from the confidence interval about the weight?

b) Which confidence level gives a width on the confidence interval of 5 gram?

c) How large sample size do you need to have if confidence interval width should be 5 gram and the confidence level is 95%. Assume that the estimated standard deviation is the same as in a).