Stat 100

[Alex]

I'm hesitant to provide assistance on these since they are essentially vocabulary questions and it has been a long time since I've worried about the precise definitions of the terms being asked about.

That said:

Researchers asked a sample of 50 1st grade teachers and a sample of 50 12th grade teachers how much of their own money they spent on school supplies in the previous school year. They wanted to see if teachers at one grade level spend more than teachers at the other grade level.

a. What type of study is found—observational or randomized experiment? Explain. – This study is an observational experiment. The subjects are the teachers, and the amount of personal money they spend on school supplies is being observed.
b. What is the experimental unit? – The experimental unit is the teachers
c. What is the response variable? – The response variable is the money spent
d. What is the explanatory variable? – The explanatory variable is the teachers from different grade levels.
e. Do we have to worry about confounding variables in this instance? Why? If so identify a possible confounding variable? Yes, we have to worry about confounding variables in this example. Confounding variables are found in observational experiments. The confounding variable may be the amount of discretionary money each teacher has to spend.
f. Are either of the terms retrospective study or prospective study relevant? Explain. This study would be a retrospective study – the teachers are asked to recall how much of their own money they spent in the previous school year.

A. I think you're correct that it is an observational study, but the reason isn't so much that you're observing something (you're always observing something) but rather because the experimental units (teachers) are not randomly assigned to the explanatory variable (grade level of teacher).
B. Correct.
C. Correct.
D. Correct.
E. Correct. This type of question screams for an expectation that something will be quoted from the text book, so I wouldn't know if you have. However, I don't think you can state that "confounding variables are found in observational experiments." They are more common in them but they can exist in randomized experiments as well and it is possible for an observational experiment to not have them. But you do always have to try and consider them.
F. Correct.

For your second question I must be missing something because I don't see how enough information is provided to answer most of the questions about it. I don't see where an experiment is being described, just methods for gathering data.