I'm looking at collecting information on whether participants playing an educational game on a particular topic will achieve lower/comparable/superior gains between pretest/post-test scores compared to participants who learn that subject matter without a game (lecture only). Thus, I intend to randomly assign participants to one of two groups: game or no game.
Each participant will take a pretest and post-test.
Assume the results are as follows: all participants from both groups score an average of 50% on the pretests, the participants who play the game have an average post-test score of 90%, and the participants who don't play the game (lecture only) have an average post-test score of 70%. With the correct statistical technique and "enough" participants, it might suggest that the game made a difference.
Additionally, I also plan on examining whether gender affects pretest/post-test scores (thus, should I have four groups? Male/game, Male/no game, Female/game, Female/no game) I'll likely also look at other demographics like age (categories to be determined, but assume: age 20-40/game, 20-40/no game, 41-60/game, etc.)
Unfortunately, it's been over 20 years since I had a stats course. What technique do I use for these types of calculations (ANOVA?), and how many participants do I need in each category for the results to be valid? Additionally, what confidence interval is normally considered "valid"? 95%? 99%?