The **mean** and **standard deviation** (std. dev.) characterize the normal
density curve. The mean is the center point of the density curve. Below, three std. dev.
to the left and to the right of the mean are marked on the graph axis. To change these
parameters type in the desired value(s) and press the **Update** button. By default
the mean is set equal to 0 and the std. dev. is set equal to 1 (i.e., "Standard
Normal Density").

The curve **tails** are delimited by the two vertical green flags. The tail values
can be set by clicking on a flag and dragging. Notice that a flag's value is displayed
at the top of each flag. If the **2-Tail** checkbox is checked the tails are
locked symmetrically around the mean.

The applet calculates the area shaded dark yellow under the curve. To find the proportion
of values **less than** a given value, drag the left flag to that value. Similiarly, to find
the proportion of values **greater than** a given value, drag the right flag to
that value. For the proportion **between** two values, drag the right flag to the
smaller value, and the left flag to the larger value.