Question

x= white cell count per mL^3 of whole blood.
\[\mu =7500\]
\[\sigma=1750\]
I get...
P(z<-2.29)

how did they get...
=0.0110

Answer 1

P(z< -2.29) is asking for the probability of z being less than -2.29 standard deviations below the mean.

This calculator shows
http://davidmlane.com/hyperstat/z_table.html
that the area (out a total of 1) below -2.29 is 0.0110

Answer 2

Click on the button "below". Fill in -2.29 for the value. A small region on the left will be filled in blue. that is the area, and it corresponds to the probability...

Answer 3

btw, I had to reload the site to get it to respond