Percent Error (Time)
📚 What You'll Learn
- What percent error means: the proportional difference between prediction and actual
- Finding the difference between predicted and actual time using absolute value
- Building a table to estimate 100%, 10%, 5%, and 1% error
- Comparing your difference to the table to estimate percent error
In this example, I'm being asked to predict how many seconds it will take this vehicle to travel a distance of four meters.
Looking at the equation and the graph, I predict that the car will take 15.79 seconds to travel four meters.
When I ran the vehicle for that distance, I found the actual time was 16.93 seconds, so my prediction was off by a little over one second. Is being off by one second good?
Well, it varies. If I predicted our car would take three seconds and it actually took two seconds, that one second has a much larger proportion than if I predicted the car would take say 30 seconds and it actually took 29 seconds.
In order to determine if a prediction is good, we're going to need to look at it in proportion to the actual results and use something called: percent error.
Percent error is the proportional difference between a prediction and what actually occurs.
I'm going to use this table to help me estimate my error percentage.
In this example, the vehicle traveled a distance of four meters. I predicted it would take 15.79 seconds to complete that distance while it actually took 16.93 seconds.
Now I need to find the difference.
To find the difference, subtract the actual time from the predicted time. Then take the absolute value.
For this, I'm going to use a calculator.
The absolute value of that is one and fourteen hundredths.
And now for percent error. The percent error is calculated from actual time.
One hundred percent error means I would have been off by 16.93 seconds.
To find ten percent error, I just need to find one tenth of one hundred percent. That's equal to 1.69 seconds when rounded to the nearest hundredth.
If I know ten percent error, I can find five percent error because five is half of ten.
.85 seconds.
And I can find one percent error by taking one-tenth of the ten percent error time.
.17 seconds when rounded to the nearest hundredth.
So to estimate my percent error, I can compare these percentages with the difference.
In this example, my percent error is somewhere between five percent and ten percent.