Further Studies are Needed for Testing the Effects of Topical Conditioned Medium of Stem Cells in Facial Skin Nonsurgical Resurfacing Modalities for Antiaging

Abstract

We would like to respond to the commentary with further understanding of the issue of potential statistical power in the analysis of our original finding. This further analysis has been planned to be carried out using the data from the wrinkle outcome because it has been contributed by the largest sample size with a dramatic effect size among all outcomes. Sequential analysis in this letter has been down with alpha 0.05 (type I error) and power of 0.80 (1—type II error) based on the O’Brien Fleming method. In addition to the common settings abovementioned, we chose a small effect size (SMD = 0.2) for avoiding underestimation in the optimal information size calculation and power analysis. The analysis was conducted using R via RStudio. The figure of sequential analysis shows that the cumulative effect of topical CM of stem cells on wrinkle outcome reaches statistical significance (z score of the end of blue line > 2), which is consistent with our original finding. Nevertheless, the information size of the outcome is insufficient (n = 118), which is lower than the required sample size (n = 1419). The observed power of the effects of topical CM of stem cells on the wrinkle outcome is only about 0.64, which is lower than the pre-defined or expected power of 0.80. Based on the fraction of information, although the observed z score of 3.232 for the cumulative effect surpasses 2, it does not surpass the monitoring boundary of 6.795 at the fraction (8.3%).

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