An article in Nature Genetics [(2003, Vol. 34(1)], Treatment-Specific Changes in Gene Expression Discriminate in vivo Drug

An article in Nature Genetics [(2003, Vol. 34(1)], €œTreatment-Specific Changes in Gene Expression Discriminate in vivo Drug Response in Human Leukemia Cells,€ reported the results of a study of gene expression as a function of different treatments for leukemia. Three treatment groups are mercaptopurine (MP) only, low-dose methotrexate (LDMTX) and MP, and high-dose methotrexate (HDMTX) and MP. Each group contained ten subjects. The responses from a specific gene are shown in Table 13E-3.

(a) Check the normality of the data. Can you assume that these samples are from normal populations?

(b) Take the logarithm of the raw data and check the normality of the transformed data. Is there evidence to support the claim that the treatment means differ for the transformed data? Use α = 0.1.

(c) Analyze the residuals from the transformed data and comment on model adequacy.

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Treatments Observations MP ONLY 334.5 69.6 67.5 882.1 62.7 120.7 31.6 404.2 701 41.2 61.2 66.6 881.9 MP+ HDMTX 919.4 1024.8 54.1 191.1 671.6 242.8 354.2 321.9 62.8 91.1 MP+ LDMTX 26.1 69.7 290.4 108.4 240.8 396.9 23.6