Arsenic occurs naturally in very low concentrations. In healthyhuman adults arsenic blood concentrations are approximatelyNormally distributed with mean 3.9 ?g/dL (micrograms per decilitre)and standard deviation 1.4 ?g/dL. For the purposes of thisquestion, assume that the distribution of arsenic bloodconcentrations is exactly as just described.
(a) What proportion of healthy adults have arsenic bloodconcentrations between 2 and 4.5 ?g/dL?
b) Choosing a healthy adult at random, what is the chance thattheir arsenic blood concentration exceeds 6.8 ?g/dL?
(c) What are the lower and upper limits of the middle 80% ofarsenic blood concentrations in healthy human adults?
