Physics » The Nature of Physics » Approximation

Summary and Main Ideas

Summary of lessons so far

The following are the main ideas from the lessons so far:

  • Accuracy of a measured value refers to how close a measurement is to the correct value. The uncertainty in a measurement is an estimate of the amount by which the measurement result may differ from this value.
  • Precision of measured values refers to how close the agreement is between repeated measurements.
  • The precision of a measuring tool is related to the size of its measurement increments. The smaller the measurement increment, the more precise the tool.
  • Significant figures express the precision of a measuring tool.
  • When multiplying or dividing measured values, the final answer can contain only as many significant figures as the least precise value.
  • When adding or subtracting measured values, the final answer cannot contain more decimal places than the least precise value.
  • Scientists often approximate the values of quantities to perform calculations and analyze systems.

Glossary of Words


the degree to which a measured value agrees with correct value for that measurement


an estimated value based on prior experience and reasoning

Method of adding percents

the percent uncertainty in a quantity calculated by multiplication or division is the sum of the percent uncertainties in the items used to make the calculation

Percent uncertainty

the ratio of the uncertainty of a measurement to the measured value, expressed as a percentage


the degree to which repeated measurements agree with each other

Significant figures

express the precision of a measuring tool used to measure a value


a quantitative measure of how much your measured values deviate from a standard or expected value

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