Bless you Sir! thank you for your response if the third column and the axis is :

**Sum(from r = 1 to r = x) of xP(X = r)**Why is it saying :

**Sum( xP(X <= r) )**?

There is the less than equal to symbol which is throwing me off. Lets include this in the errata?

The heading for the third column is misleading (or maybe just plain wrong!)

The third column is the sum of the values in the second column, up to that value of x. It is like a cumulative expectation.

0.2

0.2 + 0.32

0.2 + 0.32 + 0.384

...

A better heading might be:

**Sum(from r = 1 to r = x) of xP(X = r)**

but using sigma notation.

The book has another stab at the notation as the label to the vertical axis of the graph at the bottom of the page. There the sigma symbol is included, but I still think it's slightly odd notation.