Drug content assessment. Scientists at GlaxoSmithKline Medicines Research Center used high-performance liquid chromatography (HPLC) to determine the amount of drug in a tablet produced by the company (Analytical Chemistry, December 2009). Drug concentrations (measured as a percentage) for 50 randomly selected tablets are listed in the table below and saved in the accompanying file.

a. Descriptive statistics for the drug concentrations are shown at the top of the XLSTAT printout on the next page. Use this information to assess whether the data are approximately normal.

b. An XLSTAT normal probability plot follows (next page). Use this information to assess whether the data are approximately normal. HPLC

a. b.

c. Normal probability plots for Exercise 4.119 91.28 92.83 89.35 91.90 82.85 94.83 89.83 89.00 84.62 86.96 88.32 91.17 83.86 89.74 92.24 92.59 84.21 89.36 90.96 92.85 89.39 89.82 89.91 92.16 88.67 89.35 86.51 89.04 91.82 93.02 88.32 88.76 89.26 90.36 87.16 91.74 86.12 92.10 83.33 87.61 88.20 92.78 86.35 93.84 91.20 93.44 86.77 83.77 93.19 81.79 Source: Based on P. J. Borman, J. C. Marion, I. Damjanov, and P. Jackson, “Design and Analysis of Method Equivalence Studies,” Analytical Chemistry, Vol. 81, No. 24, December 15, 2009 (Table 3).