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CHAPTER 3.3
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Agreement
First, it was tested whether outcomes of results of parameters differed between methods of
analysis. Therefore, mixed models were fitted in MlwiN 2.02 for the outcome variables lnCONC and
MORF with “method of analysis” (SQA vs. LM) as fixed effect and “Stallion” as random effect, the
latter to adjust for clustering of ejaculates within stallion. For extended semen, mixed models were
fitted for the outcome variables TM and PM with “method of analysis” (CASA vs. LM and SQA vs. LM,
respectively) as fixed effect and “Stallion” as random effect, the latter to adjust for clustering of
ejaculates within stallion.
Second, scatter plots plotting the values of SQA-Ve and CASA against LM, respectively, were
created, as well as the corresponding Bland-Altman plots.
3.3.4. Results
3.3.4.1. Raw semen
Repeatability of SQA-Ve
None of the parameters changed significantly over time (Table 1). The repeatability of
lnCONC was excellent. The linear regression line fit to the data approached the line of perfect
agreement and the corresponding Bland-Altman plot had narrow 95% limits of agreement (Fig. 2).
Repeatability for MORF and the three motility parameters on the other hand was rather poor as
shown in Fig. 2 for MORF and PM. All CVs were acceptable (