This comment only applies to those of us who are lucky enough to come out ahead on a given visit to the casino. In my case, this happens only 15% to 20% of the time. One way to measure your effectiveness in terms of winning is to calculate the ratio of your net winning at the end of the visit to the total of all "substantial" payouts (more on that below). For instance, if you get a good jackpot on your first spin and you leave the casino immediately, your effectiveness would be 100%.
The difficult part is to define a substantial payout. For high-limit players, one can define it as any handpay. For example, in the thread by Lizzybee in the section "The Biggest Winners" dated September 11, her net winning was $40,000 and the total of her handpays was $200,000. So her effectiveness was 20%.
For other players, one can define a substantial payout as a reasonable multiple of their bet size. I will use my last casino visit as an example. My bet size was typically $5 per spin. So I arbitrarily chose 60 times my bet size as a measure of a substantial payout. By adding all payouts of $300 or more, I came up with the figure $6,000. Since, I left the casino that day with a net gain of $1,500 my effectiveness was 25%.
I should admit that this was my highest effectiveness rate to date as it is very difficult usually to keep a high percentage of your winnings (except if you are lucky enough to get a jackpot several thousand times your bet size). What was helpful that day was that I got two handpays. Although I got about a hundred handpays through the years, this was only the second time that two handpays occurred the same day.