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?

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