Seems there's only one relationship that facilitates meaningful comparisons
of scoring effectiveness in advantaged situations.  It's the relationship
between how much opportunity (time) a team has to score power play goals
and how many times they succeed.  The numerator is minutes:seconds and the
denominator is PP goals.  There's no need to distinguish between minor and
major penalties.  I would compute one "PP Opportunity Second" for each
one-man advantage during each tick of the game clock , so that periods of
two-man advantage would record two PP Opportunity Seconds per clock second.

In the following example, (which displays 3 games and the cumulative 3-game
total for a single team) the meaningful item for comparison is the last
one.  I'd prefer to see all four reported as game statistics, but the first
three aren't necessary for comparing PP scoring efficiency.

               Game1     Game2   Game3  CumulTot
PP Situations      7         6       8        21
PP Time         9:15     10:09    7:43     27:07
PP goals           2         0       2         4
PP Time/goal    4:38  [10:09/0]  03:52      6:47

Having tried the exercise with various scenarios, I pity the official
scorer/timekeeper who has to run those numbers on an immediate basis.  That
takes at least a laptop and a pre-existing spreadsheet template to turn out
reliable results when penalty action gets busy..  I suspect, one day, there
could be scholarship athletes working toward their BSs in Penalty
Statistics Management.

boB Griebel