Chapter 2. Measurement, Units and Data

The International System of Units (SI) is the global standard. Base units include the metre (length), kilogram (mass), second (time), ampere (electric current), kelvin (temperature), mole (amount of substance) and candela (luminous intensity) [5].

Accuracy and precision. Accuracy is closeness to the true value; precision is the repeatability of measurements.

Significant figures show the reliability of a measurement. Report no more digits than the measurement justifies.

Scientific notation. 300,000 = 3 × 10⁵ and 0.0042 = 4.2 × 10⁻³.

Graphs and data. Plot the independent variable on the horizontal axis and the dependent variable on the vertical axis. Label axes with units. Look for trends, but remember that correlation does not prove causation [1].

Uncertainty. All measurements have error. Repeating trials and taking the mean reduces random error; calibrating instruments reduces systematic error.

Review: Convert 2.5 km to metres. (Answer: 2,500 m.)