Post-test effects of positive psychology interventions on psychological well-being. The square boxes show effect size and sample size (the larger the box, the larger the sample size) in each study, and the line the 95% confidence interval. The diamond reflects the pooled effect size and the width of the 95% confidence interval.
Bolier et al. BMC Public Health 2013 13:119 doi:10.1186/1471-2458-13-119