2.8.5. Data Screening and Transformation
SECONDARY
In the analyses of primary and secondary parameters, a significant deviation from the normal distribution was examined. Additional investigations were conducted to find the skewness as a measure of how symmetrically the observed values were distributed about the mean. Some transformations to logarithmic scales were applied to these parameters on the basis of the skewness sign in order to avoid data loss due to rank order in non-parametric tests and to achieve normal distribution if possible.Furthermore, an attempt was made to use an additional approach to evaluate the change between the start and the end of the study. Instead of the evaluation of ∆(V3-V1), ANCOVA with values at V3 as the dependent variable and baseline (V1) values as the covariate was performed. The aim was to compare the real study effect at the study end with exclusion of the baseline values’ influence. This was possible, e.g., in the analysis of the absolute body fat mass (BFM; kg), because the prerequisites for normality and homoscedasticity were given.