The characteristics of sweet potato chips fried at different temperatures were investigated in the Journal of Food Engineering (September 2013). A sample of 6 sweet potato slices were fried at 130° using a vacuum fryer. One characteristic of interest to the researchers was internal oil content (measured in millions of grams). The results were: x̅ = 178 and s = 11. The researchers are interested in estimating the variance of the interval oil content measurements for sweet potato chips.

a. Identify the target parameter, in symbols and words.

b. Compute a 95% confidence interval for σ2.

c. What does it mean to say that the target parameter lies within the interval with "95% confidence"?

d. What assumption about the data must be satisfied in order for the confidence interval to be valid?

e. To obtain a practical interpretation of the interval, part

b, explain why a confidence interval for the standard deviation, σ, is desired.

f. Use the results, part b, to compute a 95% confidence interval for σ. Give a practical interpretation of the interval.