Abstract
Mean difference can be used as an effect size measure if the outcome variable has the same unit of measurement for both the treatment/intervention and placebo/control groups. The raw mean difference can be scaled by the inverse variance weight to define weighted mean difference (WMD). Unlike the SMD, the WMD retains the same unit of measurement as the outcome variable.
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References
Borenstein M, Hedges LV, Higgins JP, Rothstein HR (2010) A basic introduction to fixed-effect and random-effects models for meta-analysis. Res Synth Methods 1(2):97–111
Cochran WG (1973) Experiments for nonlinear functions (R.A. Fisher Memorial Lecture). J Am Stat Assoc 68(344):771−781. https://doi.org/10.1080/01621459.1973.10481423
DerSimonian R, Laird N (1986) Meta-analysis in clinical trials. Control Clin Trials 7(3):177–188
Doi SA, Barendregt JJ, Khan S, Thalib L, Williams GM (2015a) Advances in the meta-analysis of heterogeneous clinical trials I: the inverse variance heterogeneity model. Contemp Clin Trials 45(Pt A):130–138. https://doi.org/10.1016/j.cct.2015.05.009
Doi SA, Barendregt JJ, Khan S, Thalib L, Williams GM (2015b) Advances in the meta-analysis of heterogeneous clinical trials II: the quality effects model. Contemp Clin Trials 45(Pt A):123–129. https://doi.org/10.1016/j.cct.2015.05.010
Doi SA, Barendregt JJ, Khan S, Thalib L, Williams GM (2015c) Simulation comparison of the quality effects and random effects methods of meta-analysis. Epidemiology 26(4):e42–44
Higgins JP, Thompson SG, Deeks JJ, Altman DG (2003) Measuring inconsistency in meta-analyses. BMJ 327(7414):557–560
Memon MA, Awaiz A, Yunus RM, Memon B, Khan S (2018) Meta-analysis of histopathological outcomes of laparoscopic assisted rectal resection (LARR) vs open rectal resection (ORR) for carcinoma. Am J Surg 216(5):1004–1015. https://doi.org/10.1016/j.amjsurg.2018.06.012
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Appendix 9—Stata Codes for Meta-Analysis of WMD
Appendix 9—Stata Codes for Meta-Analysis of WMD
A9.1 Blood loss dataset
Study | n_larr | mean_larr | sd_larr | n_orr | mean_orr | sd_orr | study_period |
|---|---|---|---|---|---|---|---|
Bonjer et al. (2015) | 699 | 200 | 222 | 345 | 400 | 370 | recent |
Fleshman et al. (2015) | 240 | 256.1 | 305.8 | 222 | 318.4 | 331.7 | recent |
Stevenson et al. (2015) | 238 | 100 | 111 | 235 | 150 | 181.5 | recent |
Jeong et al. (2014) | 170 | 200 | 148 | 170 | 217.5 | 185 | recent |
Ng et al. (2014) | 40 | 141.8 | 500 | 40 | 361.1 | 623 | recent |
Liu et al. (2011) | 98 | 310 | 96 | 88 | 380 | 85 | recent |
Lujan et al. (2009) | 101 | 127.8 | 113.3 | 103 | 234.2 | 174.3 | old |
Ng et al. (2009) | 76 | 280 | 500 | 77 | 337 | 423 | old |
Ng et al. (2008) | 51 | 321.7 | 750 | 48 | 555.6 | 1188 | old |
Braga et al. (2007) | 83 | 213 | 258 | 85 | 396 | 258 | old |
Zhou et al. (2004) | 82 | 20 | 19 | 89 | 92 | 25 | old |
A9.2 Stata Codes for the Blood loss dataset
. ssc install admetan
Codes for WMD meta-analysis of blood loss
. admetan n_larr mean_larr sd_larr n_orr mean_orr sd_orr, wmd
. admetan n_larr mean_larr sd_larr n_orr mean_orr sd_orr, wmd re
. admetan n_larr mean_larr sd_larr n_orr mean_orr sd_orr, wmd ivhet
A9.3 Codes for WMD Subgroup analysis of blood loss by study period
. admetan n_larr mean_larr sd_larr n_orr mean_orr sd_orr, wmd by(study_period)
. admetan n_larr mean_larr sd_larr n_orr mean_orr sd_orr, wmd re by(study_period)
. admetan n_larr mean_larr sd_larr n_orr mean_orr sd_orr, wmd ivhet by(study_period)
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Khan, S. (2020). Meta-Analysis of Weighted Mean Difference. In: Meta-Analysis. Statistics for Biology and Health. Springer, Singapore. https://doi.org/10.1007/978-981-15-5032-4_9
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DOI: https://doi.org/10.1007/978-981-15-5032-4_9
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