In our study which is completed, I have three groups: Drug A (n=87), Drug B (=62) and Drug C (n=5). The Shapiro-Wilk test, histograms and side-by-side box plots were used to assess normality of the data of the individual groups with respect to all the parameters used separately (weight, BMI, blood sugar, total cholesterol, triglycerides, LDL-cholesterol, HDL-cholesterol, clinical / illness / adverse effect / quality of life, etcc, scores).
So, ultimately we check for non-normal distribution and outliers, and are concerned about unequal sample sizes (n=5 in the Drug C group), in addition to looking at descriptive statistics (mean ± SD and proportion of % wherever applicable), nonparametric tests were carried out for the inference: For between-group comparisons, Kruskal Wallis H and subsequently for the therapeutic effect where p<0.05 obtained in Kruskal Wallis H, Mann Whitney U test as post-hoc test were used. And in case of within-group comparisons, Freidman’s test (for five evaluable visits data) and subsequently for p<0.05 for the therapeutic effect where p<0.05 was obtained in Freidman’s test, Wilcoxon-signed rank test as post-hoc test were done and p<0.05 was obtained using Wilcoxon-signed rank test in two (out of three) groups. Also, to ascertain the between-group significance difference, Mann Whitney U test was applied.
Kindly advise me:
- First of all, have I made the right choice of tests and am I going in right direction?
- With regards to the present analytical sample of N=154 in total, for arriving at final conclusion should I depend on descriptive or inferential statistics or both?
- In the case where the mean ± SD changes and proportion of percentage (%) are found comparatively higher in case of Drug C which has sample size n=5 compared to other two drug groups but in case of between-group and/or within group inferential statistical analysis, (wherever) found non-significant difference / change in case of Drug C, can it be ‘said’ superior to other two drugs ‘on the basis of descriptive statistics’ or can I at least make a statement that mean ± SD and proportion of % changes at endpoint (or at other time-point) compared to baseline were found higher in case of Drug C compared to other two or other one? So, what should be the (cautious) interpretation / statement in case of Drug C compared to other two drugs?