Effects of dietary n-3 polyunsaturated fatty acids and ... - FINS

Ash content, %1 st WorkshopXIII International Feed Technology SymposiumCentral and dispersion parameters were estimated based on two repeated measurementsperformed by the TGA and gravimetric methods. Mean, SD, range, CV, and confidenceinterval values are presented in Table 1. The existence of a certain bias between thesetwo methods is obvious, whereas the TGA method gave higher values for ash contentthan did the gravimetric method (Table 1, Fig. 3). The differences in obtained resultsmay be affected by different equipment used, different measurement conditions,uncertainties of mass equipment and temperature controllers, computation effects,operator effects and random variation. Moreover, different subsamples were used toconduct the TGA and gravimetric analyses of crude ash content. The range, SD, andconfidence interval values were smaller for the gravimetric method [2, 12].161412108640 20 40 60 80 100 120 140SampleTGA methodGravimetric methodFig. 3. Comparable overview of the results for ash content obtained by the TGA andgravimetric methodThe MANOVA test (P < 0.001) and discriminant analysis (P < 0.001) applied pointedout that there were significant differences between the crude ash content values obtainedby the TGA and gravimetric methods (Table 2). The position of confidence intervals(95% confidence limits) of the ash content results obtained by the TGA method (ellipse1) and gravimetric (ellipse 2) methods plotted in two-dimensional space (Fig. 4)indicated the existence of clearly defined boundaries between the results of two methods.Also, the position of the ellipses confirmed the existing of the certain bias between thetwo methods. The orientation of the ellipses indicates that there is strong correlationbetween the two series of data, whilst the shape of the ellipses indicates that the TGAmethod yielded more precise results in comparison to those obtained by the gravimetricmethod. This was expected since there is less sources of measurement uncertainties inthe case of the TGA method.195