Posted by Ann on Sunday, October 14, 2012 at 12:10pm.
Assume that the average annual salary for a worker in the United States is 300,000 and that the annual salaries For Americans are normally distributed with a standard deviation equal to $7,000. Find the following:
A. What percentage of Americans earn below $22,000?
B. What percentage of Americans earn above 42,000?

Statistics  David Q/R, Sunday, October 14, 2012 at 1:45pm
I'm going to assume that you mean the average annual salary is $30k, not $300k  because $300k sounds a bit excessive to me, even for Americans! If so, the proportion of Americans who earn below $22k should be the area to the left of ($22k$30k)/$7k = 1.143 in a set of Normal tables, which is 12.7%. The same sort of calculation for b) gives the area to the right of ($42k$30k)/$7k = 1.714, which is the same as 1  (area to the left of 1.714) = 1  0.957 = 4.3%.