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Statistische analyse van de groei van de rat bij het semi-chronisch toxiciteitsonderzoek met propylgallaat

Statistical analysis of the growth of the rat in the semi-chronic toxicity experiment with propylgallate

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Synopsis

This report describes an alternative statistical method for the growth of rats in semi-chronic toxicity-experiments. The new method is compared with the standaard method using the results of the semi-chronic toxicity experiment of propylgallate. The standard method is analysis of variance applied to the body-weight after each period, the cumulative grotwth after each period and the growth within each period followed by Dunnett's t-test for comparison between dose groups and control. The alternative method used is curve-fitting. With this method all measurements of the body-weight in the experimental period for each animal are reduced to three parameters which describe the curve in time. Disadvantages of the previously used method are that no account is made for the fact the results within each period are not independent, that more tables have to be generated and that a large number of tests have to be done. The large number of tests together with the dependent results within each period can lead to illogical patterns by spuriously significant differences. The curve-fitting method resulted in a curve which adequately described the data and did not give rise to heterogeneous residuals. The results are summarized more succinctly in one tabel and of the fitted parameters A and Q have a good biological interpretation so that direct information is available over the real growth. Treatment effects on the fitted constants could be analysed with ANOVA with Dunnett's t-test.
 

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