Why make Prop Bets on the NFL?
Why are some prop bets considered easier than side/totals bets on NFL games? The Sportsbooks often offer props as a marketing tool rather than as a means of profit. Think of how many times you have heard of some crazy prop bet on the news. That is free advertising for the casino. Because of the large number of prop bets offered on NFL games there really isn’t the time available to spend on each one. Think of it, the line maker still has other sports to put up lines on like the NHL, NBA, MLB …etc.
That is why prop bets are more a formulaic practice than actual line making. How is a line made for the over/under betting on how many passing yards a quarterback will have?
It is a relatively simple formula.
The average passing yards per game multiplied by (opposing defenses average passing yards allowed after / the leagues average passing yards allowed)
Of course this alone can be misleading if the quarterback had one huge passing game and distorted the average passing yards per game. This is why the median must be developed. The median is the middle number of passing yards by the quarterback. If there is an even number of games then add the two middle numbers together and divide by two. After that compare the medium to the mean to determine which is a more accurate portrayal of the quarterbacks performance.
An example of the medium and the mean for a quarterback from Tom Brady’s passing yards for the first 5 games of the 2015 season.
- 312 yards
- 275 yards
- 358 yards
- 466 yards
- 288 yards
The mean is 339 (this is the total number of yards divided by the number of games). The median is 312 (this is the number in the middle of the range of numbers).
A quick analysis is needed to decide which is better: mean or median? If we see that he had 466 yards because he was in a shootout with the Bills and was forced to throw the entire game, it explains why the average (mean) is higher. But both are relatively close. For the year Brady averaged 298 per game. Now you have a guide to look at when the number comes out for your prop bet. The next step would be to take either the medium or the mean and complete the formula by the defense allowed part of the formula. For some this will seem like quite a bit of math but the important point is this is about all the sportsbook manager will do when it comes to setting a line. With over 70 prop bets on your average NFL game and hundreds available on playoff games this quick calculation is all he has time for. He will offset the lack of a true line by adding to the vig (often -115 / -115), and reduced betting limits.
The reduced limits and general lack of action does one more thing to the line. It can move the line with far less money being bet on one side. For example, someone bets $500 wager Manning to throw for less than 280 yards at -115. The line might move to (-105 / -125). The move will depend on how much action there is on the line. Because these lines are often automated and do not require the sportsbook manager to set the line. All he has to do is approve the computers line move. The important thing to take away is there will be many variations in the line at different books. This is unlike the side/total which is heavily bet and tends to settle within a point.
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