Question: Researchers were interested the vitamin C content of a food commodity called wheat soy blend (WSB), which is often mixed with other ingredients and cooked. Loss of vitamin C as a result of this process was the major concern of the researchers. One preparation used in Haiti called gruel (or “bouillie” in Creole) can be made from WSB, salt, sugar, milk, banana, and other optional items to improve the taste. Samples of gruel in Haitian households were collected. The vitamin C content (in milligrams per 100 grams of blend, dry basis) was measured before and after cooking. Here are the results:

Sample 1 2 3 4 5
Before 73 79 86 88 78
After 20 27 29 36 17

Set up appropriate hypotheses and carry out a significance test for these data. (It is not
possible for cooking to increase the amount of Vitamin C). Calculate the appropriate summary statistics that are needed ( n , x , and s ).