Many consumers pay careful attention to stated nutritional contents on packaged foods when making purchases. It is therefore important that the information on packages be accurate. A random sample of n = 12 frozen dinners of a certain type was selected from production during a particular period, and the calorie content of each one was determined. (This determination entails destroying the product, so a census would certainly not be desirable!) Here are the resulting observations, along with a boxplot and normal probability plot. (To obtain the dataset for your analysis software, go to the Book Companion Website.) 255 244 239 242 265 245 259 248 225 226 251 233
(a) Is it reasonable to test hypotheses about true average calorie content μ by using a t test? Yes, it is reasonable. No, t test is not applicable here. It depends on the results of t test.
(b) The stated calorie content is 241. Does the boxplot suggest that true average content differs from the stated value? Yes, it is clear that true average content differs from the stated value. No, it is possible that true average content is 241. There's not enough evidence to decide.
(c) Carry out a formal test of the hypotheses suggested in part (b). (Use Table 4 in Appendix A. Use α = 0.05. Round your test statistic to two decimal places and your P-value to three decimal places.) t = df = P = Conclusion: Reject H0. Fail to reject H0.