In this study, we investigate how Wilks’ lambda, Pillai’s trace, Hotelling’s trace, and Roy’s largest root test statistics can be affected when the normal and homogeneous variance assumptions of the MANOVA method are violated. In other words, in these cases, the robustness of the tests is examined. For this purpose, a simulation study is conducted in different scenarios. In different variable numbers and different sample sizes, considering the group variances are homogeneous σ12=σ22=⋯=σg2 and heterogeneous (increasing) σ12<σ22<⋯<σg2, random numbers are generated from Gamma(4-4-4; 0.5), Gamma(4-9-36; 0.5), Student’s t(2), and Normal(0; 1) distributions. Furthermore, the number of observations in the groups being balanced and unbalanced is also taken into account. After 10000 repetitions, type-I error values are calculated for each test for α = 0.05. In the Gamma distribution, Pillai’s trace test statistic gives more robust results in the case of homogeneous and heterogeneous variances for 2 variables, and in the case of 3 variables, Roy’s largest root test statistic gives more robust results in balanced samples and Pillai’s trace test statistic in unbalanced samples. In Student’s t distribution, Pillai’s trace test statistic gives more robust results in the case of homogeneous variance and Wilks’ lambda test statistic in the case of heterogeneous variance. In the normal distribution, in the case of homogeneous variance for 2 variables, Roy’s largest root test statistic gives relatively more robust results and Wilks’ lambda test statistic for 3 variables. Also in the case of heterogeneous variance for 2 and 3 variables, Roy’s largest root test statistic gives robust results in the normal distribution. The test statistics used with MANOVA are affected by the violation of homogeneity of covariance matrices and normality assumptions particularly from unbalanced number of observations.
[Purpose] The effects of vitamin D on the circulating levels of IL-17 and IL-13 were
investigated in patients with diabetic peripheral neuropathy, patients with diabetes
mellitus type 2 without neuropathy, and healthy controls. [Subjects and Methods] A
single-blind controlled clinical study was performed, including70 type 2 diabetic patients
with or without diabetic peripheral neuropathy and 33 healthy volunteer controls. The
25(OH)D levels were evaluated using ultra-performance liquid chromatography, and IL-17 and
IL-13 levels were assessed using enzyme-linked immunosorbent assays. [Results] The 25(OH)
vitamin D concentration was lower in diabetic peripheral neuropathy patients than in
diabetes mellitus patients without neuropathy and healthy controls. Similarly, 25(OH)D
levels were lower in diabetes mellitus patients than healthy controls. IL-17 and IL-13
levels were higher in diabetes mellitus patients than in controls. Additionally, IL-13
levels were higher in diabetic peripheral neuropathy patients than in diabetes mellitus
patients without neuropathy. These differences were statistically significant. There was a
significant positive correlation between 25(OH)D and IL-13,and a negative correlation
between 25(OH)D andIL-17 in the diabetic and diabetic neuropathy groups. [Conclusion]
Vitamin D is a potential modifiable risk factor for diabetic peripheral neuropathy and may
regulate inflammatory mediators, e.g., IL-17 and IL-13.
There is an association between obesity and several inflammatory and oxidative markers in children. In this study, we analyzed thiol/disulfide homeostasis and serum ischemia-modified albumin (IMA) levels for the first time in order to clarify and determine the oxidant/antioxidant balance in metabolically healthy and unhealthy children. Methods: This study included obese children and healthy volunteers between 4-18 years of age. The obese patients were divided into two groups: metabolically healthy obese (MHO) and metabolically unhealthy obese (MUO). Biochemical parameters including thiol/ disulfide homeostasis, and IMA concentrations were analyzed. Results: There were 301 recruits of whom 168 (55.8%) were females. The obese children numbered 196 (MHO n=58 and MUO n=138) and healthy controls numbered 105. No statistically significant difference could be found in ages and genders of the patients among all groups (p>0.05, for all). Native thiol (SH), total thiol (SH+SS), and native thiol/total thiol (SH/SH+SS) ratio were statistically significantly lower in the MUO group than the control group (p<0.001, p=0.005, and p=0.005; respectively). Disulfide (SS), disulfide/native thiol (SS/SH), disulfide/total thiol (SS/SH+SS) and IMA levels were statistically significantly higher in the MUO group than the control group (p=0.002, p<0.001, p<0.001, and p=0.001, respectively). Conclusion: Chronic inflammation due to oxidative stress induced by impaired metabolic parameters in MUO children caused impairment in thiol redox homeostasis. Our data suggested that the degree of oxidant imbalance in obese children worsened as obesity and metabolic abnormalities increased. It is hypothesized that thiol/disulfide homeostasis and high serum IMA levels may be reliable indicators of oxidant-antioxidant status in MUO children.
The purpose of this study was to implement the BBD method, which is a response-surface method, quantitatively and compare it with three-way analysis of variance. In the study, we used the shortform The World Health Organization Quality of Life WHOQOL-BREF-TR scale, which was developed by the World Health Organization and was tested by Eser et al. (1999) to determine its validity and reliability. This approach allowed us to attempt to determine the optimal variable combination in the psychological quality of life of mothers with intellectually-disabled children. The research was conducted with 540 mothers who had intellectually-disabled children. By use of 3 3 Box Behnken experimental design (BBD), which is a response surface method, variables and levels were determined according to the balanced incomplete block design. According to the results, the main effects of the mother's age and the number of children were statistically significant. In addition, the interaction effect of "the mother's age*the time she learnt the disability" was significant. The R 2 value of the model was found to be 90.33%. When the same set of data was analyzed via three-way analysis of variance, both the main effects and the interaction effects were found to be insignificant. The response surface method may be an alternative to the analysis of variance in the factorial experiments that are used frequently in the social sciences and in research related to social work.
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