The accompanying data resulted from an experiment to compare the effects of vitamin C in orange juice and in synthetic ascorbic acid on the length of odontoblasts in guinea pigs over a 6-week period (“The Growth of the Odontoblasts of the Incisor Tooth as a Criterion of the Vitamin C Intake of the Guinea Pig,” J. of Nutrition, 1947:

491–504). Use the Wilcoxon rank-sum test at level .01 to decide whether true average length differs for the two types of vitamin C intake. Compute also an approximate P-value.

Orange Juice 8.2 9.4 9.6 9.7 10.0 14.5 15.2 16.1 17.6 21.5 Ascorbic Acid 4.2 5.2 5.8 6.4 7.0 7.3 10.1 11.2 11.3 11.5