# Graphing a P-P plot given a set of data from a Poisson distribution?

I'm attempting to complete an assignment for a class and reading the book isn't particularly helpful as it's extremely wordy and unclear. I'm mainly confused on exactly what the x and y values are supposed to be within a P-P plot. The problem I'm given is as follows:

If the following data are hypothesized to be drawn from a Poisson distribution:

3, 0, 7, 2, 6, 4, 3, 4, 3, 4, 5, 0 0, 3, 2, 1, 0, 3, 4, 4, 7, 2, 3, 6 2, 1, 2, 2, 1, 1, 3, 0, 3, 4, 3, 5

Draw a P-P plot for the distribution.

The book states something along the lines of:

A probability–probability (P–P) plot is a graph of the model probability $Fˆ(X_{(i)})$ versus the sample probability $F˜_{n}(X_{(i)}) = q_i,$ for i = 1,2,...,n

Based on earlier assignments, it's my understanding that $F˜_{n}(X_{(i)}) = \frac{i-0.5}{n}$, but what is the formula for $Fˆ(X_{(i)})$? And which belongs on which axis?

• You might find this answer here informative. – mdewey Nov 27 '16 at 14:11