Xylitol has proven effective in preventing dental caries (cavities) when included in food or gum. A total of 75 Peruvian children were given milk with and without xylitol and were asked to evaluate the taste of each. The researchers measured the children’s ratings of the two types of milk. (Source: Castillo JL, et al (2005) Children's acceptance of milk with xylitol or sorbitol for dental caries prevention. BMC Oral Health (5)6.)

a.   What is the response variable in this experiment?

b.   Think of some of the factors in the study. Which are controlled? Which factor is manipulated?

c.   What are the treatments? How many treatments are there?

d.   How are factors that are not controlled or manipulated dealt with?

e.   What type of experimental design is this?

f.    Identify the subjects