Groups that created more correct ideas (correct contributions or CCs) might be more likely to solve a problem, and students' recent actions (micro-time context) might aid CC creation. 80 high school students worked in groups of 4 on an algebra problem. Groups with higher mathematics grades or more CCs were more likely to solve the problem. Dynamic multilevel analysis statistically identified watersheds (breakpoints) that divided each group's conversation into distinct time periods with many CCs versus few CCs, and modeled the groups' 2,951 conversation turns. Wrong contributions, correct evaluations of one another's ideas, justifications, and polite disagreements increased the likelihood of a CC. In contrast, questions, rude disagreements, and agreements reduced it. Justifications had the largest effects, whereas the effects of correct evaluations lasted 3 speaker turns. Some effects differed across groups or time periods. In groups that solved the problem, justifications were more likely to yield CCs, and questions were more likely to elicit explanations. Meanwhile, the effects of agreements and correct evaluations on CCs differed across time periods. Applied to practice, teachers can encourage students to evaluate others' ideas carefully and politely, express and justify their own ideas, and explain their answers to group members' questions. (Contains 4 figures and 10 tables.)