Our best guess of the cumulative probability of a data point in a set of observations turns out to be r/(n+1) where r is the rank of the data point within the data set and n is the number of observations. Thus, when choosing this option, one needs to:
- Rank the observations in ascending order;
- In the column to the left of the observations, calculate the rank of the data: write a column of values 1, 2, … n;
- In the column immediately to the right of the data, calculate the cumulative probability F(x) = rank/(n+1);
- Use the data and F(x) columns as inputs to the distribution.
Note that the minimum and maximum values of x only have any effect on the very first and last interpolating lines to create the Cumulative distribution, and so the distribution is less and less sensitive to the values chosen as more data are used in its construction.