Statistical analysis
assumptionas
The collected data were statistically analyzed with a software program (IBM SPSS Statistics, v20.0, IBM Corp, New York, USA) (α = 0.05). Initially, the normality was tested for the quantitative data with Shapiro-Wilk test showing that data being normally distributed if One-way ANCOVA reveled the following assumptions: Linearity assumptionas shown in Fig. 
Grouped Scatterplot for marginal gap
Simple scatterplot predicted values versus standardized residuals