Arsenic in Toenails Arsenic is toxic to humans, and people can be exposed to it

Question

Arsenic in Toenails Arsenic is toxic to humans, and people can be exposed to it through contaminated drinking water, food, dust, and soil. Scientists have devised an interesting new way to measure a person’s level of arsenic poisoning: by examining toenail clippings. In a recent study,1 scientists measured the level of arsenic (in mg/kg) in toenail clippings of eight people who lived near a former arsenic mine in Great Britain. The following levels were recorded: 0.8 1.9 2.7 3.4 3.9 7.1 11.9 26.0 1Button, M., Jenkin, G.,Harrington, C., and Watts, M., ‘‘Human Toenails as a biomarker of exposure to elevated environment arsenic,’’ Journal of Environmental Monitoring, 2009; 11(3): 610–617. Data are reproduced from summary statistics and are approximate. (a) Do you expect the mean or the median of these toenail arsenic levels to be larger? Mean Median SHOW HINT (b) Calculate the mean. Round your answer to one decimal place. Meanequals mg/kg Calculate the median. Enter the exact answer. Medianequals mg/kg

Explanation / Answer

Given Data:

0.8, 1.9, 2.7, 3.4, 3.9, 7.1, 11.9, 26.0

a) Since the maximum value i.e. 26 seems to be an outlier, we expect that mean would be greater than median.

Mean is the answer.

b) Mean

= (Sum of Observations) / (Number of observations)

= 57.7 / 8

= 7.2 (Rounded off to one decimal place)

c) Number of observations = 8 (Even)

So,

Median

= Average of 4th and 5th term

= (3.4 + 3.9)/2

= 3.65

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