The graph that I attached (in post #57) illustrates (as we know) that there are many factors that influence SAC rates. I decided to see if I could quantify some of the many effects on my SAC rate with the data that I keep in my log (which, conveniently, is actually a spreadsheet). Factors that I wanted to try to measure the effect of (and that I had data on) were:
Experience (as measured by cumulative number of dives, as shown in the graph) and by cumulative number of dives in a given type of exposure protection (i.e., cumultive number of wetsuit dives or drysuit dives)
Diving Wet or Dry (as shown in the graph)
Minimum water temperature of the dive
Average depth of the dive
Maximum depth of the dive
Number of days since last dive (in any kind of exposure protection)
Number of days since last dive with the same kind of exposure protection (e.g., if I am analyzing drysuit dives, the number of days since my last drysuit dive).
I explain my results below (and attach a PDF file of the computer output for anyone who is interested in the details of the regression analysis).
I could not get reliable estimates for the effect of any variable listed above that is not also listed below.
What I found was:
An increase of 100 dives decreases my SAC when diving wet by about 10%. (Using just number of wet dives---instead of all dives---does not provide as good a fit to the data.)
An increase of 100 dives decreases my SAC when diving dry by about 27%. (Using just the number of dry dives---instead of all dives---does not provide as good a fit to the data.)
A decrease in the minimum temperature by 10 degrees Fahrenheit increases my SAC by about 7 percent for dry dives (but I could not get a reliable estimate for wet dives).
100 days between dives (not that I've gone that long!) increases my SAC by 12 percent for wet dives (but I could not get a reliable estimate for dry dives).
These factors combined explain only between 30% and 40% of the variation in my SAC rates, so there is more variation unexplained (i.e., unquantified) then there is explained.
Since I have never seen any estimates like this before, I do not know how reasonable they are. But the direction of all these effects makes sense to me, as does the relative magnitudes of the experience effect on wet versus dry diving. It also makes sense to me that minimum temperature affects my dry dives but not my wet ones (since all my wet dives are "warm" [i.e., range is 71-83 degrees, with an average of 78] while some of my dry dives are uncomfortably cold [38-66 degrees, with an average of 53]).
