3.2.17. Statistic Evaluation and Correlation Analysis

Data and diagrams were prepared with Prism 7 (Version 7.0) and 9 (Version 9.1) from GraphPad Software Inc. (San Diego, CA, USA) and presented as means with standard deviations (SD) of at least three independent experiments if not stated otherwise. For the display of dose–response graphs in the GPx1 assay, the 95% confidence interval was included instead of the SD. Assessment of statistical significance was performed via ANOVA (analysis of variation) coupled with a Dunnett’s or Tukey’s multiple comparisons test and significance levels expressed as * p < 0.05, ** p < 0.01, *** p < 0.001, or **** p < 0.0001.

To analyze a putative correlation between potency and cell doubling times, we used the Pearson correlation calculation of Prism 7 or 9 (GraphPad Software, San Diego, CA, USA). It was assessed to what extent two variables vary together, in this case X was either the IC₅₀ from MTT or GI₅₀ from crystal violet assay and Y was the doubling time of the respective cell line. Results are output as correlation efficient r with the corresponding p-value as level of significance. For interpretation of the r-values, we applied a common scale: 0.0–0.1 negligible, >0.1–<0.4 weak, 0.4–<0.7 moderate, 0.7–<0.9 moderate, >0.9 strong [36].