That, my friends, is the "normal" bell curve. The curve pretty much everything everywhere falls into. But what does it show us exactly?

Lets take a peek at how its devided up...

OK... so between the red lines lies 68% of all data.

between the Green lines lies 95% of all data.

between the Yellow Lines lies 99.7% of all data.

Now what these sections show us is not JUST the % of data within each sections.

Between any two z-scores chosen along the axis of the curve we can find the are, the percentage AND a probability all in one.

On another point, remeber how befor we had to worry about window settings and clearing pictures ans so on jsut to find the ara between two z-scores? Well frett no more. Mr.K showed us the quick-fast way to do it. Get your calculators ready...

STEPS :

-ON

-2nd

-VARS

-2

You will then on your home screen see somthing that looks like "normalcdf( ". At this point, you type in your z-scores (lowest,highest) OR your range, mean then the standard deviation.. in that order , seperated by commas... like so (low end of the range,high end of the range, mean, standard deviation).

-Don't forget to CLOSE the bracket! )

Quick example of the FIRST way using the Z-scores.

Ex 1. Q. Given the Z scores -.2 and 1.4, what percentage of the data lies in that particular range?

A. normalcdf(-.2,1.4)

*hit enter*

The number you get is 0.4985

That number gives you three things.

-The area between those two numbers is .4985

-The percent of data within those two numbers (49.85%)

-The probability that of all the data collected, that something would be "picked" out of that specific section.

What the question asked for was percentage... so your answer would be **49.85%**

Next example of the OTHER way by using the range, mean and standard deviation.

Ex 2. Q. A selection of numbers has been aquired. Given a high of 190 and a low of 160, a mean of 150 and a standard deviation of 10, what is the probability that a selected number from a particular group of numbers is within that range?

A. normalcdf(160,190,150,10)

*hit enter*

You get **0.1586**

Final thing we used was the Reverse norm function. It is a function we have that allows us to find the z score using the area.

STEPS:

-ON

-2nd

-VARS

-3

At this point you enter in the area/persentage/prabability.

Well that about summs it up. Gnight.

Next scribe is Eugene.

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