Mercury is a persistent and dispersive environmental contaminant found in many ecosystems around the world. When released as an industrial by-product, it often finds its way into aquatic systems where it can have deleterious effects on various avian and aquatic species. The accompanying data on blood mercury concentration (mg/g) for adult females near contaminated rivers in Virginia was read from a graph in the article "Mercury Exposure Effects the Reproductive Success of a Free-Living Terrestrial Songbird, the Carolina Wren" (The Auk, 2011: 759-769; this is a publication of the American Ornithologists' Union).

a. Determine the values of the sample mean and sample median and explain why they are different. [ˆ‘x1 = 18.55.]
b. Determine the value of the 10% trimmed mean and compare to the mean and median.
c. By how much could the observation .20 be increased without impacting the value of the sample median?

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20 22 .25 .30 .34 41 55 .56 .42 1.70 1.83 2.20 2.25 3.07 3.25