SOLUTION: Using the z-table (Table E), find the critical value (or values) for a a=.018 left-tailed test.

We need to find a cut off point on the left of the curve, like
the black line segment below:



so that the area under the curve to the left of that cut-off
point will be .018.  

However table E only gives the areas between the y-axis and the
cut-off point.  Since there is area of .5 on the whole left side
of the y-axis, and there is to be area .018 to the left of that
cut-off point, then there will be area of .5-.018 or .482 between
the y-axis and the cut-off point.  So we look in the BODY of the
table, until we find the closest value to .482.  The closest value
in Table E to .482 is .4821.  We find that value where you see 2.1
under the z-column and .00 at the top of the column .4821 is in.

So the answer is z = -2.1. You have to make it negative because it
is a left-tail test and the numbers are negative on the left side
of the curve.

Edwin