The averages and standard deviations of several subgroups in a study are sometimes need to be combined in meta-analysis, the calculating method to do this was given in this paper. Firstly, a commonly used incorrect calculating method to do the combination was pointed out; it origins from metrology and should be applied in the combination of standard deviations of several groups of measurements of the same object, and it's not fit for the combination of several subgroups' data in meta-analysis. Meanwhile the calculating error of this method was tested with real and constructed data and its impact on the conclusion of meta-analysis was analyzed. The incorrect method may result in a big calculating error with the real research data and even lead to an incorrect conclusion with the constructed data. The correct formula was deduced and given, the calculating result of the correct formula equals the true value when neglecting the round error. The error analysis of the incorrect method was then done with the correct formula and an accurate combination result can only be got when meeting the condition given by this paper. The correct method in this paper should be used to combine standard deviations in the future researches.
Citation：
ZHANGBing, KANGJie, CHENXiao-ming. Methods to Combine Standard Deviations of Different Subgroups in Meta-analysis. Chinese Journal of Evidence-Based Medicine, 2016, 16(7): 851-854. doi: 10.7507/1672-2531.20160130
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Copyright © the editorial department of Chinese Journal of Evidence-Based Medicine of West China Medical Publisher. All rights reserved
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- 1. Kaplowitz K, Bussel II, Honkanen R, et al. Review and meta-analysis of ab-interno trabeculectomy outcomes. Br J Ophthalmol, 2016, 100(5):594-600.
- 2. Klamann MK, Gonnermann J, Maier AK, et al. Influence of selective laser trabeculoplasty (SLT) on combined clear cornea phacoemulsification and trabectome outcomes. Graefes Arch Clin Exp Ophthalmol, 2014, 252(4):627-631.
- 3. Ting JL, Damji KF, Stiles MC, et al. Ab interno trabeculectomy:outcomes in exfoliation versus primary open-angle glaucoma. J Cataract Refract Surg, 2012, 38(2):315-323.
- 4. Belovay GW, Naqi A, Chan BJ, et al. Using multiple trabecular micro-bypass stents in cataract patients to treat open-angle glaucoma. J Cataract Refract Surg, 2012, 38(11):1911-1917.
- 5. Toteberg-Harms M, Hanson JV, Toteberg-Harms J. Cataract surgery combined with excimer laser trabeculotomy to lower intraocular pressure:effectiveness dependent on preoperative IOP. BMC Ophthalmol, 2013, 13:24.
- 6. Wikipedia Contributors. Pooled Variance. Wikipedia[cited 2016 Jan 15]. Available at:https://en.wikipedia.org/w/index.php?title=Pooled_variance&oldid=684787717.
- 7. 丁香园站友.两组数据合并后的均数和标准差如何计算.丁香园[cited 2016 Jun 15]. Available at:http://www.dxy.cn/bbs/topic/8661245.
- 8. IUPAC. Assignment and Presentation of Uncertainties of the Numerical Results of Thermodynamic Measurements (provisional). PureApplChem, 1981, 53(9):1805-1826.
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- 11. 吴红梅, 杨茗.数据提取.见:刘鸣, 主编.系统评价、Meta分析设计与实施方法.第1版.北京:人民卫生出版社, 2011:90.
- 12. 杨亚琼, 陈宁, 郭建, 等.蛇毒类血凝酶用于外科手术切口有效性和安全性的系统评价.中国循证医学杂志, 2015(11):1309-1316.
