NAME:

Does bread lose its vitamins when stored? Small loaves of bread were prepared with flour that was fortified with a fixed amount of vitamins. After baking, the vitamin C content of two loaves was measured. Another two loaves were baked at the same time, stored for three days, and then the vitamin C content was measured. The units are milligrams per hundred grams of flour (mg/100g). Here are the data (provided by Helen Park; see Helen Park et al., "Fortifying bread with each of three antioxidants", Cereal Chemistry, 74(1997), pp. 202-206).) (Example taken from Introduction to the Practice of Statistics, 3^rd Ed., David S. Moore and George P. McCabe.)

Immediately after baking: 47.62, 49.79

Three days after baking: 21.25, 22.34

When bread is stored, does it lose its vitamin C? We won't actually perform the formal statistical test here, but I'm interested in making sure you know what steps to do. For each answer, be sure to explain.

a) Would you use a paired test or a two-independent groups test?

b) What test statistic would you use?

c) What assumptions are you making?

d) What is the sampling distribution of this test statistic?

e) Do the data suggest that the variances of the two populations are equal? (Don't do a formal test. Just give me an informed opinion.)