## B.1 When the \(z\)-score is known, and the area is sought

The table gives the probability (area) that a \(z\)-score is **less** than the \(z\)-score looked up.
For example:
Look up \(z = -1.87\); the area *less than* \(z = -1.87\) is about 0.0307,
or about 3.1%.

To use this table,
enter the \(z\)-score in the search box *under* the `z.score`

column.
The area will be shown.
The table includes \(z\)-values between -4 and 4.
(Alternatively, you can search through the table manually.)

The online Tables work with two decimal places.
As an example, then, consider finding the area to the *left* of \(z=-2.00\).
In the tables,
the value `-2`

is entered in the search region, just under the column labelled `z.score`

(see the animation below).
After pressing `Enter`

,
the answer is shown in the column headed `Area.to.left`

:
the probability of finding a \(z\)-score less than \(-2\) is 0.0228, or about 2.28%.

The hard-copy tables work differently.
On the tables,
look for \(-2.0\) in the *left* margin of the table,
and for the second decimal place (in this case, 0)
in the *top* margin of the table
(see the animation below):
where these intersect is the area (or probability) *less than* this \(z\)-score.
So the probability of finding a \(z\)-score less than \(-2\) is 0.0228, or about 2.28%.