Macular degeneration is the most common cause of blindness in people older than 60 years. One variable thought to be related to a type of inflammation associated with this disease is level of a substance called soluble Fas ligand (sFasL) in the blood.
The accompanying table contains representative data on x = sFasL level for 10 patients with age-related macular degeneration. These data are consistent with summary quantities and descriptions of the data given in the paper “Associations of Plasma-Soluble Fas Ligand with Aging and Age-Related Macular Degeneration” (Investigative Ophthalmology & Visual Science [2008]: 1345–1349).
The authors of the paper noted that the distribution of sFasL level was skewed and recommended a cube-root transformation. The cube-root values and the normal scores for a sample size of 10 are also given in the accompanying table.
- a. Construct a normal
probability plot using the untransformed data. - b. Does the normal probability plot for the untransformed data appear linear or curved?
- c. Construct a normal probability plot using the cube-root transformed data. Does the normal probability plot appear more nearly linear than the plot for the untransformed data?
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Chapter 7 Solutions
INTRODUCTION TO STATISTICS & DATA ANALYS
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