For each of the following examples (the same as in Exercise 7.41), state the null hypothesis and the research hypothesis, in both words and symbolic notation:

a. A researcher is interested in studying the use of antibacterial products and the dryness of people’s skin.

He thinks these products might alter the moisture in skin compared to other products that are not antibacterial.

b. A student wonders if grades in a class are in any way related to where a student sits in the classroom. In particular, do students who sit in the front row get better grades, on average, than the general population of students?

c. Cell phones are everywhere and we are now available by phone almost all of the time. Does this translate into a change in the nature or closeness of our long-distance relationships?