In an experiment to accelerate a trolley along a runway, a light gate measured the time the trolley took to pass through it. There were five repeats of the same acceleration test and it took the following readings: 0.87s, 0.89s, 0.65s, 0.76s, 0.77s. Which of these is the correct percentage error for this set of time readings?
A: 0.12% B: 0.15% C: 15% D: 30%
The answer is C, can someone explain why/how you calculate percentage error in this context?