Six different national brands of chocolate chip cookies were randomly selected at the supermarket. The grams of fat per serving are as follows:9;9;11;7;8;8. Assume the underlying distribution is approximately normal.

NOTE: If you are using a Student'st-distribution, you may assume that the underlying population is normally distributed. (In general, you must first prove that assumption, though.)

• Part (a)
• Construct 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. (Round your answers to two decimal places.)
• (ii) Sketch the graph.
• (iii) Calculate the error bound. (Round your answer to two decimal places.)