Six different national brands of chocolate chip cookies were randomly selected at the supermarket. The grams of fat per serving are as follows:
8; 8; 10; 7; 9; 9.
Assume the underlying distribution is approximately normal.
a. Calculate a 90% confidence interval for the population mean grams of fat per serving of chocolate chip cookies sold in supermarkets.
i. State the confidence interval.
ii. Sketch the graph.
iii. Calculate the error bound.
b. If you wanted a smaller error bound while keeping the same level of confidence, what should have been changed in the study before it was done?
c. Go to the store and record the grams of fat per serving of six brands of chocolate chip cookies.
d. Calculate the mean.
e. Is the mean within the interval you calculated in part (a)? Did you expect it to be? Why or why not?