Meta-analysis is a statistical method to compare and combine effect sizes from a pool of relevant empirical studies. It is now a standard approach to synthesize research findings in many disciplines, including medical and healthcare research. This paper is the third paper of a mini-series introducing systematic review and meta-analysis. First, common effect sizes used in meta-analysis are presented. Fixed-, random- and mixed-effects models are then introduced. Next, a real data set from a published meta-analysis will be used to illustrate the procedures and interpretations. Last, software packages that may be used to conduct meta-analyses will be highlighted.

The compounds, TiO 2 -1 & -2 were synthesized by 0.5 M NaNO 3 : 0.5 M KNO 3 (I) and 0.88 M LiNO 3 :0.12 MLiCl (II) salts at 510 • C and 280 • C, resp.., XRD studies show single anatase phase with characteristic tetragonal lattice parameter values of a ∼3.78 Å and c ∼ 9.51 Å. The TEM images show aggregates of 10-30 nm sized nanosquares (TiO 2 -1) and spherical particles (TiO 2 -2). Surface area of the TiO 2 powders were 74 and 200 m 2 g −1 , resp. for 1 and 2. Upon heat-treatment (TiO 2 -2) from 500 • C to 850 • C, the surface area decreases from 80 to 0.7 m 2 g −1 . Cyclic voltammetry studies show cathodic and anodic peaks at ∼1.7 and ∼ 2.0 V, resp. for both bare and heat treated TiO 2 up to 750 • C. Galvanostatic cycling studies show that the first discharge-charge capacity values are 244 and 198 (±3) mAh g −1 resp. for TiO 2 -1 at a current of 33 mA g −1 in the voltage window, 1.0-2.8 V vs. Li/Li + . TiO 2 -2 nanoparticles show a less capacity fade during cycling and delivered first discharge-charge capacity values of 340 and 253 (±3) mAh g −1 , resp. at a current rate of 33 mA g −1 . The effects of heat-treatment and Li-cycling at a cutoff voltage (0.005 V) were studied and discussed reaction mechanism.

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Co3O4 was prepared in aqueous solutions through a staged oxidation process. When the mole ratio of starting chemicals Co2+:OH− is ≤1:2 (Co2+ as a limiting reagent), the formation reaction follows the brucitelike phase to cobalt oxide-hydroxide, and then to cubic spinel. However, when the ratio of Co2+:OH− is > 1:2 (OH− as a limiting reagent), the reaction path changes to the brucite-like to hydrotalcite-like phase, and then to the spinel. Using the present method, Co3O4 can be formed at a temperature as low as 40 °C, and single-phase spinel Co3O4 can be prepared at 50 °C within hours under normal atmospheric pressure.