Variance, fluctuations and the usual

From Bootlegger's good work, here in the glossary...

'Fluctuations' "This word describes the ups and downs of your bankroll."

'Variance' "This can be determined by subtracting the expected value from each possible outcome in a game or hand, squaring the differences and multiplying each square by its probability of occurring and then summing the total of the product."

Sorry Boot; it's not your fault that I sure am no math nerd, but your description for variance flies way over my head.
There was some discussion here just recently on these, and as usual in BJ forums, much gnashing of teeth over them, which is why I began with Boot's word definitions, so we can all be on the same page.

Now I, for one would like to hear say, another (simpler?) explanation of variance; and without the use of math-nerd terms. (No disrespect, Boot!)

My own (uneducated) explanation is this: (For the moment, leaving out shuffle-tracking, sequence-remembering, ace-tracking and the like.)

Nobody can predict the flow of card sequences, which I don't think anyone will deny. So even if the count is in my favor, and I am but one of 6 players, (7 including the dealer) I must get 'lucky' to get what I want, when I want it, correct? Keep in mind the other 5 players are also expecting what they want, too. Some of us must miss out, obviously. Variance. (Makes me want to go back to baseball betting!)

Bottom line. Anybody else have an explanation/definition that I can almost understand?

What's the problem?

"You must not get 'unlucky' to get what I want, when I want it, correct"

is more like it.

I'm no math nerd either and I had to sit down and work out step-by-step the definition I stole from Professional Blackjack to understand it.

Here's a possible non-math way to look at it. The Rocky Mountains have a mean (average) altitude. Now we know that there will be many mountains higher than that average and many lower than the average. The Great Plains also has an average altitude, but you won't find much difference between the lowest point and the highest point. The variance, that is the average of the squared distance away from that mean for each mountain in the range, or each possible altitude in the Great Plans, would be great for the Rockies and not so great for the Great Plains.

The greater the variance, the greater the individual highs and lows will be. The smaller the variance, the smaller the highs and lows.

Put simply, the larger your variance, the greater the probability that you will be losing even though you have a positive expectation.

Now for some, maybe simple, math. If take the square root of the variance you get the standard deviation (SD).

Given an expected value (EV), 68% of the time your actual result will be between EV-SD an EV+SD. 95% of the time, it will be between EV-2SD and EV+2SD and 99% of the time between EV-3SD and EV+3SD.

The US just having just finished an election cycle, you probably have heard of the margin of error in polling. This probably refers to 2 standard deviations in the polls.

Variance is a mathematical term. In fact it is a number with a precise definition. As a non math-geek, you might not understand derivatives or integrals either, but you wouldn't want someone to explain calculus in non-math terms, would you?

Variance is a number that can be calculated for any random variable, if you know all about its distribution. Once you have that number, you can make all kinds of fancy predictions about what might, or might not, happen with that random variable -- particularly if the variable happens to be "normally distributed," which it often is for repeated trials.

In other words, variance helps us quantify luck. For example, you need the variance (among other things) in order to calculate "risk of ruin" to any given bankroll. Blackjack players talk a lot about risk of ruin.

ETF