Obscure Probability Question > Suppose that blood chloride concentration (mmol/L) has a normal distribution with mean 104 and standard deviation 5 (information in the article “Mathematical Model of Chloride Concentration in Human Blood,” J. of Med. Engr. and Tech., 2006: 25–30, including a normal probability plot as described in Section 4.6, supports this assumption). > > a.What is the probability that chloride concentration equals 105? Is less than 105? Is at most 105? > > b.What is the probability that chloride concentration differs from the mean by more than 1 standard deviation? Does this probability depend on the values of $\sigma$ and $\mu$ > > c. How would you characterize the most extreme .1% of chloride concentration values? I am having trouble with part c). I'm just not quite sure what it is asking.

I guess you should find out the range of the lowest $0.05\%$ of all values, and similarily the range of the highest $0.05\%$ of all the values. The first range will have the form $(-\infty,a)$, and the second range will have the form $(b,\infty)$.