### Standard Normal
Distribution

Always start
each new problem from the home screen

When calculating the
probability of an event using the **Normal Distribution Function**
there are two main categories from which you may choose on the
calculator:

**1.** **Standard Normal ( using
Z-scores)**

**2. Normal (using the raw data). **

We
will first discuss the **Standard Normal Distribution.**

Lets say we want to find the area under the curve
between **z = -1** and **z = 1**.

This
is the probability that an event is "within 1 standard deviation of
the mean." We know from the Empirical Rule that this probability
should be about 68%. On the calculator we need to go to the
distributions menu.

First press __ __(you should see this screen)

Highlight __"2 : normalcdf( "__ and press (see screen below)

We need to enter only two
values into the parenthesis.

They must be in this order: **lower limit, ____
upper limit ) **

So for our problem we will enter

*Remember the
negative symbol is the *__gray button__ not the __blue
button__**.**

__.6826894809__ will be displayed. This is the probability
that an event will fall within **1** standard deviation of the mean
value. Or stated another way it is the area under the Standard Normal
curve between **-1** and **1**.

To see a **graph **of
this same problem we first need to adjust the WINDOW.

So press (this screen will appear)

Make sure **your** settings match the above screen.

Next
return to the distributions menu. Go back to this screen:

From this
screen **Arrow right** and highlight
"__DRAW " __. Notice that __"1 : ShadeNorm(
"__ is Highlighted. Press ** ** (see screen below)

We need to
enter the same two pieces of data in the same order. So we will

Enter

Now press (see screen below)

Notice that this graph gives the area as well as the lower, and upper
limits.

[You can find the area under the curve between any two
Z-scores using either one of these methods just described.]

*
If your Z-scores fall below -4, or above 4 then you will need to adjust
the **X-Min**, and **X-Max** in the
WINDOW menu to fit your Z-scores. *

To clear this screen
press ** **

** "clrdraw**" will be
highlighted.

Press ** **This will clear the
drawing** **.