Treating psoriasis with the “Doctorfish of Kangal.” Refer to the Evidence-Based Research i...

Treating psoriasis with the “Doctorfish of Kangal.” Refer to the Evidence-Based Research in Complementary and Alternative Medicine (Dec. 2006) study of treating psoriasis with ichthyotherapy, presented in Exercise Treating psoriasis with the “Doctorfish of Kangal.” Psoriasis is a skin disorder with no known cure and no proven effective pharmacological treatment. An alternative treatment for psoriasis is ichthyotherapy also known as therapy with the “Doctorfish of Kangal.” Fish from the hot pools of Kangal, Turkey, feed on the skin scales of bathers, reportedly reducing the symptoms of psoriasis. In one study, 67 patients diagnosed with psoriasis underwent three weeks of ichthyotherapy. ( Evidence-Based Research in Complementary and Alternative Medicine , Dec. 2006). The Psoriasis Area Severity Index (PASI) of each patient was measured both before and after treatment. (The lower the PASI score, the better is the skin condition.) Box plots of the PASI scores, both before (baseline) and after three weeks of ichthyotherapy treatment, are shown in the accompanying diagram. a. Find the approximate 25th percentile, the median, and the 75th percentile for the PASI scores before treatment. b. Find the approximate 25th percentile, the median, and the 75th percentile for the PASI scores after treatment. c. Comment on the effectiveness of ichthyotherapy in treating psoriasis.

 (Recall that the therapy is also known as the “Doctorfish of Kangal,” since it uses fish from the hot pools of Kangal, Turkey, to feed on skin scales.) In the study, 67 patients diagnosed with psoriasis underwent three weeks of ichthyotherapy. The Psoriasis Area Severity Index (PASI) of each patient was measured both before and after treatment. (The lower the PASI score, the better is the skin condition.) Before- and aftertreatment PASI scores were compared with the use of the Wilcoxon signed rank test. a. Explain why the PASI scores should be analyzed with a test for paired differences. b. Refer to the box plots shown in Exercise Suppose that 40 and 90 are two elements of a population data set and that their z -scores are -2 and 3, respectively. Using only this information, is it possible to determine the population’s mean and standard deviation? If so, find them. If not, explain why it’s not possible.

Give a reason that the researchers opted to use a nonparametric test to compare the PASI scores. c. The p -value for the Wilcoxon signed ranks test was reported as p 6 .0001. Interpret this result, and comment on the effectiveness of ichthyotherapy in treating psoriasis.