The following data on distilled alcohol content (%) for a sample of 35 port wines was extracted from the article "A Method for the Estimation of Alcohol in Fortified Wines Using Hydrometer Baumé and Refractometer Brix" (Amer. J. Enol. Vitic., 2006: 486–490). Each value is an average of two duplicate measurements 16.35 18.85 16.20 17.75 19.58 17.73 22.75 23.78 23.25
19.08 19.62 19.20 20.05 17.85 19.17 19.48 20.00 19.97
17.48 17.15 19.07 19.15 19.90 18.68 18.82 19.03 19.45
19.20 18.00 19.60 19.33 21.22 19.50 15.30 22.25
a. Determine the value of the IQR.
b. Are there any outliers in the sample? Any extreme outliers?
c. Construct a boxplot and comment on its features.
d. By how much could the largest observation be decreased without affecting the value of the IQR?