A student finds the acceleration due to gravity with a pendulum and gets 9.65 m/s²…

Step 1. Absolute. $|9.65\ \text{m/s}^2 - 9.80\ \text{m/s}^2| = 0.15\ \text{m/s}^2$.

Step 2. Relative. $\dfrac{0.15\ \text{m/s}^2}{9.80\ \text{m/s}^2} = 0.0153$.

Step 3. Percentage. $0.0153 \times 100\% = 1.53\%$.