When a poultry farmer uses her regular feed, the chickens attain normally distributed weights with a mean of 1.77 kg. In an experiment with an enriched feed mixture, nine chickens are born that attain the weights (in kg) given below.

a. Use a 0.01 significance level to test the claim that the mean weight is higher with the enriched feed.
b. If the farmer can charge an extra 2 cents for each additional gram that her chickens weigh, and if it will cost an extra $1.17 per chicken to feed them the enriched feed, is it a good decision to switch to the enriched feed?
Use the traditional approach summarized in Figure 7-4. Draw a graph showing the test statistic and critical values. In each case, assume that the population has a distribution that is approximately normal and that the sample is randomly selected.

1.74 1.77 1.90 1.80 1.88 1.87 1.79 1.81 1.89