The article “The Accuracy of Stated Energy Contents of Reduced-Energy, Commercially Prepared Foods” (J. of the Amer. Dietetic Assoc., 2010: 116–123) presented the accompanying data on vendor-stated gross energy and measured value (both in kcal) for 10 different supermarket convenience meals):
Meal: 1 2 3 4 5 6 7 8 9 10 Stated: 180 220 190 230 200 370 250 240 80 180 Measured: 212 319 231 306 211 431 288 265 145 228 Carry out a test of hypotheses based on a P-value to decide whether the true average % difference from that stated differs from zero. [Note: The article stated “Although formal statistical methods do not apply to convenience samples, standard statistical tests were employed to summarize the data for exploratory purposes and to suggest directions for future studies.”]