The researchers want to examine whether a mindfulness intervention is effective, compared to the control group where participants did not receive any intervention. Which of the following results would indicate that the mindfulness intervention is effective?
1) The spreads of the distributions differ, with the mindfulness group having more spread or variability
2) The centers of the two distributions differ, with the mindfulness group centered at a lower value
3) The centers of the two distributions differ, with the mindfulness group centered at a higher value
4) The centers of the two distributions are about the same