please answer the following bolded questions! thanks!

Dr. Rogers wanted to test a new "sing-along" method to teach math to eighth graders (e.g., "I love to multiply" to the tune of "God Bless America"). He recruited teachers from a local middle school to participate in the study. Teachers were instructed to use the sing-along method in their first period math classes, and to continue having their students solve math problems with their old method during their sixth period math classes. At the end of the term, Dr. Rogers found that the first period classes scored significantly lower than the sixth period classes on a mathematics achievement test. He concluded that the sing-along method was a total failure.

1. Identify the independent variable(s).

2. Identify the dependent variable(s).

3. Identify at least two possible confounding variables or problems with this study.

a. b.

4. Identify something Dr. Rogers could do to reduce the confounds/problems.