HARRISBURG, Pa. (WHTM) The flashing lights.

The spinning wheels.

The sound of coins hitting the tray below. A metal-on-metal clank that makes slot machines so appealing to so many.

“The biggest game that people play in casinos is slots,” said Jon Friedl of Ohio. “It’s played the most. It keeps the lights on in the casino.”

Friedl dubbed himself professor slots. He is, indeed, a college professor with a minor in slot machines. Friedl has a website and a blog devoted to slot machines. He’s won several medium-sized jackpots and a car playing slots. He admits he’s still chasing a grand prize but is also realistic.

“It’s very unlikely and it’s all based on luck,” he said.

But at some Pennsylvania casinos, Lady Luck is a bit more flirtatious. Casinos set the payout percentages on the machines.

State law requires that PA casinos payback at least 85 percent to players.

They all do more than that.

But they don’t all do the same.

Because the law also requires public posting of wagering numbers, we can tell you that in June, in 12 casinos, $2.8 billion was wagered.

$2.5 billion of it was given back in winnings.

Valley Forge casino was tops, giving back at 91.06 percent.

Parx casino was second at 90.69.

Presque Isle in Erie set its slots at 89.16 percent, lowest in the state.

Hollywood Casino at Penn National was second from the bottom at 89.44 percent.

“A percentage point here and a percentage point there and pretty soon you’re talking real money,” said Friedl.

Over time, a point or point-and-a-half difference can make a noticeable difference.

“It could end up meaning hours of gameplay because you make back a little bit of money more at one place,” Friedl said. “And you can use that to bet with, so basically stretching your dollar.”

A look at the numbers shows that when Hollywood casino opened in February of 2008 its slots payout was 91.49 percent.

By May of that year it jumped up to 92.02, its high-water mark.

Friedl says it’s common for new casinos to establish a following by letting customers win more at first.

By January of 2011, Hollywood’s payout percentage dropped below 90 percent and it hasn’t been above since.

Friedl calls that casino calculus, nothing more than a business decision.

We wanted to better understand why Hollywood chooses to set its slot machines among the lowest in the state. Management declined an on-camera interview but said in a statement of payout percentages, “It’s proprietary information that we don’t comment on for competitive reasons.”

Friedl suspects it’s a matter of competition. The casinos in Philadelphia, for instance, all set their slots above 90 percent. If players suspect they’re too low they can simply take a short drive to a competitor. Hollywood Casino at Penn National is the only game in town in its part of the state, Grantville, Dauphin County.

We did check at some of Penn National’s other Hollywood Casinos in other states and found that most of them set their slots above 90 percent.

Friedl has studied Pennsylvania casinos and run the numbers. So which one would he choose to wager his dollars?

“I would go to the one with the best buffet,” he said, only half-joking.

He noted that there are lots of reasons to go to casinos and for many people, the payout percentage of slot machines doesn’t rank high on the list.

He says there are several factors

“Do your friends go to a particular place? Does it have a good atmosphere? Do you want horse racing? Do you like musical acts or a nice hotel?

And, of course, dining options.

“I will accept a half percentage point off my payoff return if I can get myself a nice buffet.”