Erratum to: 'Chinese medicine combined with calcipotriol betamethasone and calcipotriol ointment for Psoriasis vulgaris (CMCBCOP): study protocol for a randomized controlled trial'

Erratum Unfortunately, the original version of this article [1] contained an error. The superiority margin difference should be 5 % instead of 10 %. We performed a superiority test of two independent proportions with superiority margin difference of 5 % by PASS 11.0 software again, and the results were the same as mentioned in the paper before. The sentence in the "Sample size calculation" part (Page 5) is corrected as follows: According to the supposition and as calculated by PASS 11.0 software (NCSS, LLC, Kaysville, Utah, USA), sample size of 239 in each group can achieve 90 % power and to rule out a two-sided type I error of 5 % to detect a superiority margin difference of 5 % in this two-arm trial with equal allocation in each group.