2.4. Statistical methods
Data were analyzed using SPSS 17.0 for Windows (SPSS Inc., 2008),
Excel 2007 and Access 2007 (Microsoft Corporation, 2006). Microenvironment
concentrations were tested for normality and distributions
were found to be right-skewed. Therefore geometric means and
ranges of concentrations are reported. Statistical differences between
two strata were tested in the logged database with a t-test for equality
of means and with ANOVA when testing more than two strata. Results
were considered significant with p values less than 0.05. Partial η2 was
calculated to assess the effect size of the sample in the results of the
ANOVA.