Boxes of cereal are advertised as having a net weight of 14 ounces. The weights of boxes are assumed to be normally distributed. A new cereal box-filling machine is purchased, and we wish to be sure that on average, it puts at least the correct amount of cereal in the boxes. We randomly select 16 boxes, and find they have weights with sample mean 13.5 ounces and sample standard deviation 1.1 ounces.
(a) Suppose your data included all the box weights. How would you check the normal distribution assumption? Explain what would indicate a violation of this assumption.
– You do not have to perform the check on the given data
(b) Perform a test of the null hypothesis that the average net weight of the boxes of cereal produced by the new machine is greater than or equal to 14 ounces, against the alternative that it is less than 14 ounces. What test should be used in this situation? Explain your reasoning. What is the value of the test statistic?
(c) Compute the significance probability, or p-value. Is there sufficient evidence to conclude that the new machine is under-filling the cereal boxes? Test at level α = 0.05.