What are the odds?

The internet says the odds for playing slots is 88% to 96%. That means for every $100 I play, I can expect to get back $88 to $96. Let's see what the real odds are. Each time I go to the casino, I'm going to keep track of how much I bet, my beginning balance and my final balance. From that, I should be able to calculate the actual odds for playing Vegas slots.