aTable 3 reports three different estimates of the parameters in specification (1): the pooled ordinary least squares (OLS), the between, and the fixed-effects (within) models. Though each model is based on different assumptions, all three produce an estimate of that is positive and ...
Tests of the assumptions of OLS indicate the presence of heterescedasticity and autocorrelation but the absence of unacceptible levels of multicollinearity. Based on the results of the Hausman test, a fixed effect regression analysis is used to test the model. In order to test the robustness of...
13.48 between studies ¼ 0.011), whereas for laryngeal cancer we reported the fixed-effects ones (P-value for heterogeneity between studies ¼ 0.464). Vitamin E intake was inversely related to oral and pharyngeal cancer, with an OR of 0.59 (95% CI: 0.49–0.71) for the fifth quintile ...
In all of the studies, vitamin E was expressed as α-tocopherol equivalents=weighted sum of tochopherols and tochotrienols with vitamin activity. We extracted information on its intake from natural sources (i.e., no inclusion of intakes from fortified foods), and we expressed these intakes ...
A fixed-effects model was designated to compute the pooled OR for each individual study in cases where the I2 index < 50% (p-value ≥ 0.10) [32], while a random-effects model was applied to ascer- tain within-study inaccuracies if the heterogeneity was achieved with the I2 index > ...