I experimental data for which I have four groups (1-4)with varying concentrations of a drug. The first drug has zero concentration. Each of these four groups was subdivided into two ( treated with a proinflammatory cytokine vs no treatment with a proinflammatory cytokine), so in total I have 8groups. Now my outcome of interest is il-6 concentrations in all these groups. I am interested in the relative change (ratio or think of it like how many times the il-6 increased across the various groups taking the reference in each group as the il-6 concentrations in the samples that were not simulated with pro-inflammatory cytokine). Ratios were calculated using excel. The question is how do i get standard deviations for these ratios? What is the best statistical method to determine significance in the differences across these ratios?
Dear Margaret!
In Excel, you can calculate the standard deflection for each group without cytokine stimulation and with cytokine stimulation. The mean and standard deviation are descriptive statistics and are not calculated statistically.
A statistical method is needed to calculate the statistical significance of indicators between your groups. It all depends on the number of samples in each group and whether your groups follow a normal distribution, as well as the design of your experiment. If the number of samples is small (up to 30 in each group), then it is better to use the methods of nonparametric statistics (Mann-Whitney test, Kolmogorov-Smirnov test, etc.).
If you want to compare the indicators in 2 groups in pairs, you can use the Student's t-test, but if you want to compare the IL-6 indicators with each other in all groups, then you need to use ANOVA one-way analysis (it is available for parametric and nonparametric data).
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