On page 224, I have a question about exercise #2 (Designing and Interpreting Experiments and Studies chapter in the Problem Solving and Data Analysis section). Is Ms. Carlisle’s class considered a random selection? If so, can you generalize the results from her study to only students in her class (like future ones as well) or also to all math students?

No, I don’t think you can generally assume that any school class is a random selection. For example, it could be an honors class that only students with high grades in previous math classes could have gotten into.

In that question, though, there really aren’t even any causal results to generalize. Students weren’t randomly assigned to extra help; they self-selected. You can only conclude that an intervention (extra help) is causally responsible for some outcome (higher grades) if the intervention is randomly assigned.