Small tweaks can lead to significant changes.

[nathanoj]

Over the past 6 months I've periodically increased the upper level of my pressure range just by one unit each time; 9-14, 9-15 and 9-16 cmH2O. Results in terms of AHI seemed to progressively improve but being a stats nerd I ran the numbers through a mathematical test ("One-way ANOVA") that compared the averages of the 3 groups (45 nights data in each group). Even though the decrease in average AHI was slight with each increase in max pressure, the results were statistically significant, ie a 99.9% probability that there was a real decrease, at least between the first and the 3rd group. Interesting that there was less variation in the 3rd group as shown by the height of its red bar below... meaning the individual night's AHI's  were a little more closely packed around the group average.

Will I keep tweaking? Nah... curiosity satisfied for now.