Maybe this should be in calculus instead... I'm getting reaquainted with stats and I ran across the z-table again. I always wondered how the value in the table are populated. As I understand it, the values in the table are just the value along the X axis and the corresponding area for a normal distribution. Wouldn't this be the same as find the area under the curve using an integral in calculus? I don't know the equation for the curve used in creating the z-table. Anyway, if what I said is true, then I should be able to make an equation for whatever curve is generated by the data. I made up some data below with a strong left curve. X value Y value 1 1 2 2 3 3.3 4 5 5 7 6 9 7 11 8 11 9 9 10 2 1. How do I make an equation using these data points? 2. Once I have that equation, how do I integrate? Note: I will answer Qs 1 and 2 soon. I am wondering if my original thoughts on how a z-table are created are true. When I asked in class some 2 years ago I remember my prof saying "you don't want to go into that, it's complicated"! :P Thanks PF crew!