Statistica 12.0 statistical package

The present study compared the levels of IL-6 in the serum and milk of cows with clinical and subclinical mastitis caused by Streptococcus spp. with levels in healthy cows. First, the Shapiro–Wilk test was applied to determine/exclude the normality of the distribution of trait values in the study groups. Then, the Mann–Whitney test was performed for two independent samples. p < 0.05 was considered significant. Statistica 12.0 statistical package (StatSoft. Inc., Tulsa, OK, USA) was used to perform the calculations.

The statistical analysis of the obtained results was performed using Statistica 12.0 statistical package (StatSoft, Tulsa, OK, USA) and GraphPad Prism 5.0 (GraphPad Software, Inc., La Jolla, CA, USA), with nonparametric tests: the ANOVA Kruskal-Wallis test and the Mann-Whitney test. Multiplicity adjusted p value was also calculated. The relationship between the quantitative data was assessed according to Spearman rank correlation. The results are presented as a median, minimum, maximum and percentiles. The threshold for statistical significance was p < 0.05. The sample size was set based on a previously conducted pilot study. The power of the test was set at 0.9.