00:01
Okay, here's the standard curve, the z curve, and you can see it wants the mean must be zero, and the standard deviation or the sd is 1.
00:11
And what i want is the number that cuts off the top 30 % of the z scores.
00:20
In other words, here, call it z1, this area here has to be 30%, which means the area below here, green that will be 70 % of the area or in decimal form 0 .7.
00:44
Now to find z1 what i do is use a calculator.
00:48
The ti 84 plus is a good one to use and what you do is you press second the blue button and second vars vars just below the arrow keys on the right that brings up the menu for distributions.
01:06
Is number three, which is called inverse norm.
01:11
So you want inverse norm.
01:17
You press enter and it will say area.
01:21
And that's the area left of the point i want to find.
01:24
In other words, the green area on my diagram...