Meta-analysis · continuous outcome

Forest plot example: standardised mean difference (Hedges’ g)

Forest plot of a continuous outcome from means, SDs and sample sizes per arm, pooled as a standardised mean difference with subgroups.

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ExerciseUsual careStudyMeanSDTotalMeanSDTotalWeightSMD [95% CI]AerobicAdams 201412.15.24015.35.83813.3%-0.58 [-1.03, -0.12]Baker 201610.46.15513.06.45718.7%-0.41 [-0.79, -0.04]Chen 201814.24.93215.15.03011.1%-0.18 [-0.68, 0.32]Diaz 20209.85.56113.96.06019.3%-0.71 [-1.08, -0.34]Subtotal (95% CI)18818562.3%-0.50 [-0.71, -0.29]Heterogeneity: Tau² = 0.00; Chi² = 3.13, df = 3 (P = 0.372); I² = 4%Test for overall effect: Z = 4.63 (P < 0.001)ResistanceEvans 201513.56.32814.86.1279.9%-0.21 [-0.74, 0.32]Fischer 201711.95.74414.65.94515.1%-0.46 [-0.88, -0.04]Garcia 201912.86.03613.26.23512.6%-0.06 [-0.53, 0.40]Subtotal (95% CI)10810737.7%-0.26 [-0.53, 0.01]Heterogeneity: Tau² = 0.00; Chi² = 1.59, df = 2 (P = 0.451); I² = 0%Test for overall effect: Z = 1.92 (P = 0.055)Total (95% CI)296292100.0%-0.41 [-0.58, -0.24]-2-1012Favours exerciseFavours usual careHeterogeneity: Tau² = 0.00; Chi² = 6.60, df = 6 (P = 0.359); I² = 9%Test for overall effect: Z = 4.65 (P < 0.001)Test for subgroup differences: Chi² = 1.82, df = 1 (P = 0.177); I² = 45%
Standardised mean differences in depressive symptoms, by type of exercise. Illustrative data.

About this example

When studies measure the same outcome on different scales, the standardised mean difference (Hedges’ g) puts them on a common scale. Enter the mean, SD and sample size of each arm and the effect sizes are computed for you.

Negative values favour the intervention when lower scores are better, as for depressive symptoms, so the “favours” labels are set accordingly.

The data

StudyMean TSD TN TMean CSD CN CExercise type
Adams 201412.15.24015.35.838Aerobic
Baker 201610.46.155136.457Aerobic
Chen 201814.24.93215.1530Aerobic
Diaz 20209.85.56113.9660Aerobic
Evans 201513.56.32814.86.127Resistance
Fischer 201711.95.74414.65.945Resistance
Garcia 201912.863613.26.235Resistance

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