Michael Chernick. First of I thank U very much for replying my query. I take liberty to clarify regarding my query further as follows and shall be obliged if you can help me out. This was a prospective observational study of 48 weeks comprising three groups: Drug A(n=87), Drug B(=62) and Drug C(n=5). QQ plots were also performed in addition to Shapiro-Wilk test, Histograms and Side-by-side Box plots were used to assess normality of the data of the individual group 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 etc scores). So, ultimately looking to non-normal distribution, outliers, unequal sample size (n=5 in Drug C group), in addition to descriptive statistics (mean ± SD and proportion of % wherever applicable), nonparametric tests were carried out for the inferential statistics. As far as inferential statistics, Kruskal Wallis was done for comparing independent groups (between-group difference) and Friedman RM test was done to ascertain the within-group difference between data of related pairs of baseline and endpoint as well as between data of baseline and subsequent quarterly three visits separately. The Mann Whitney U was performed as posthoc test in case wherever in Kruskal Wallis p<0.05 was obtained. So, between groups A&B, A&C and B&C. Whereas Wilcoxon Signed Rank was performed as posthoc test for assessing within-group difference wherever in Friedman RM test p<0.05 was obtained. So it was done to ascertain within-group difference between data of related pairs of individual group between baseline and endpoint data and also between and subsequent quarterly three visits (baseline & V4, baseline & V7 and baseline & V9 separately.)
What I actually wanted to ask was that was it right decision to incorporate group C(n=5) among three-groups while performing nonparametric tests (Kruskal Wallis for between independent groups and Friedman for within group comparison) or should I have kept group C(n=5) aside and done comparison among rest of the two groups? You are right in saying that ‘It appears that you want to make conclusions about the difference between the three treatment groups.’ So, in this case, the problem is if I depend on descriptive statistics (comparing the mean changes and percentage of 3 groups), due to less sample power in group C the mean changes and percentage are magnified in group C. So, what should I do? Should make comparison between 3 groups supplementing the results of inferential statistics obtained? Or Keep aside group C and make comparison between 2 groups in this case?
In case where the mean ± SD changes and proportion of percentage (%) are found comparatively higher in case of Drug C which has sample power 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 ? Thanks a lot in advance. Saurin