Fig. 8
Random-effects meta-analysis of housing effects showing overall hazard ratios and 95% confidence intervals. Subgroups are based on if animals died spontaneously or after disease induction. Blue diamond = SMD estimate (with the width reflecting the 95% CI), location of black squares indicates study hazard ratio and size indicates the weight of the study in the meta-analysis. CH = conventional housing, EH = ‘enriched’ housing, RE = random effects. I2 and Q statistic are tests of heterogeneity. Results of the model testing whether hazard ratios are significantly different from one: n = 38, z = 8.87, p < 0.0001