the Practical Skateboarder

How knowing the odds can improve your skateboarding.

Composing lines–a combination of tricks in sequence–is an essential part of skateboarding. The ability to put together lines that flow and make it looks effortless is a skill all it’s own that not every skateboarder learns how to do well. While the putting together a line that flows well with your style might be something of an art, figuring out whether you can do the line isn’t. Here, I want to lay out how any skateboarder can use just a little bit of math to figure out how difficult your line will be for you, as well as how these numbers can be used to curate your lines or inform which tricks in your lines deserve more practice.

To begin, how do you know if a combination of tricks is worth trying?

To answer this questions, you need know your success rate per trick–that is, the number of times you land a trick divided by the number of times you tried the trick. For example, if you landed 5 kickflips out of 10 attempts, then the success rate is 5/10 = 0.5 (or 50%). This number is easy enough to track over time if you’re counting and can vary with practice, increasing as you get better or decreasing when you stop practicing the trick consistently.

Now, let’s say that you’ve learned tre-flips and kickflips. Your tre-flips have a success rate of 20% since you just learned them while your kickflips have a success rate of 50% since you’ve practiced them more often. Now, you’ve got an idea for a line consisting of a kickflip followed by a tre-flip.

How likely are you to land these tricks together in a line?

To answer this question, simply multiply the success rates for each trick in the line together. Taking 0.5 (50% for your kickflips) multiplied by 0.2 (20% for your tre-flips) and you get 0.1 (10%). That is, you are 10% likely to land your tricks together and successfully complete your line.

Now, let’s say you spend a few weeks practicing your tre-flips and you increase your success rate to 50%. What are the new odds? Take 50% for your kickflip and 50% for your tre-flip, multiply the odds together, and you get 25%. Quite an improvement over the 10% before.

But maybe you’re setting your New Year’s resolution and one of your goals is to increase your success rate for your line. You think a reasonable target is 50% (and when you might have only a few attempts at your line before you get kicked out of a spot, the higher these odds, the better).

How much more do you need to improve to get your line up to a 50% success rate?

One way to get there would be to get both your kickflip and tre-flip up to a 70% success rate (0.7 x 0.7 = 0.49, just about 50%).

But let’s instead say that you’re struggling with your kickflips and getting to 70% feels like it will be an uphill battle. However, your tre-flips feel natural, almost too easy for you, and you think you can do much better than a 70% success rate. Then, instead of getting your kickflips up from 50% to 70%, it could be a better investment of your time and effort to maintain the 50% for your kickflips and keep practicing your tre-flips to get them up to nearly 100%.

What happens next if you want to add a third or fourth trick to the line–what are your odds of success? Again, simply figure out or guess the success rate for each trick independently, multiply them together, and what you’re left with is the probability of landing your three-trick or four-trick line. For example, let’s say you want to do a kickflip (50%), then a tre-flip (90%), then a 50-50 (50%) on a flat bar to end the line. Together in a line, your chances are (0.5 x 0.9 x 0.5 = 0.225) 22.5%. As more tricks are added, the likelihood of success decreases and you’ll need more tries than you may have expected.

Okay, so what’s the point of all this math and probabilities? How can you use this to get better and improve your lines?

First, if you’re thinking about how to measure your improvement as you practice, you might try keeping track of the number of trials and number of successes (your success rate). This could tell you if you’re getting better on average, and it provides a useful number to determine how a new trick could affect your lines. Simply add/substitute the trick into your lines and use the success rate to figure out the new odds.

Second, you can use these numbers to decide which tricks are worth more time and energy to improve and which may not be worth spending any more time on. It’s better to focus on the tricks that feel more natural to you and spend less time on the ones that don’t. Here, I’ve provided the numbers that back up why this is important for improving at a faster rate. If you’re thinking about a line, now you can consciously decide which tricks to keep, which tricks to stop trying, and which tricks to keep working on to increase the possibility that you land your lines consistently.

I’ll add one last thought on this subject.

It’s easy to think that just because you have a 20% success rate for landing a trick or a line that all you’ll need is 5 tries and you’re guaranteed at least 1 successful attempt (1/5 = 20%). Is that really the case though?

It turns out that if you have a 20% success rate and you’re given 5 tries to land your trick or complete your line at least 1 time that you have only a 67% chance of completing at least 1/5 of your attempts. There’s still a 33% chance that you land 0/5 of your attempts. Certainly, those odds are still in your favor, but it’s not guaranteed. The way to figure out your odds when you know the number of times you can try and your success rate is to calculate the binomial distribution. For 5 attempts and a 20% success rate, the binomial distribution is plotted in the figure below.

If you want to know more, you can learn about probability distributions of repeated trials from “A Secret Weapon for Predicting Outcomes: The Binomial Distribution” and use this online calculator provided by Matt Bognar at University of Iowa (used to make the above figure) to play around with the odds for yourself.

Why go through even more math?

This last part is simply a reminder that the world plays by odds, not guarantees. And even if the odds are in your favor, you may still end up with a bad outcome. That’s just life. Similarly, you can get lucky. Just imagine how excited you’d be if you managed to land 5/5 attempts when your previous success rate was only 20%. You had only a 0.4% chance of that happening! That would be a very lucky outcome. And it’s important to realize that it would indeed be a lucky outcome on that day. Knowing this, you can avoid fooling yourselves into thinking that you’re really better than you are.