## Uncertainty in Measurement

### Measurements are made in scientific laboratories, and are commonly used in scientific calculations. To carry out scientific calculations properly it is important to discuss the following concepts; Accuracy refers to the agreement of a particular value with the true value. Precision refers to the degree of agreement among several measurements of the same quantity. Sample animation differentiating between accuracy and precision. Exact numbers those numbers that we know exactly. Counting objects is an experiment that can be carried out with complete accuracy. Uncertainty . numbers that are not known exactly. When we measure lengths (of an object), volumes (of a liquid) or masses (of a solid) the measurements are not exact, they have some degree of uncertainty. Sample animation demonstrating uncertainty in measurement. Significant figures A useful method to express the uncertainty in measurement. Significant figure rules(see pages 20 and 21 in BLB) All nonzero digits are significant Zeros between nonzero digits are significant Zeros that precede the first nonzero digit are not significant. Reading from left to right begin counting with the first nonzero digit. Zeros are significant when they appear; in the middle of a number, at the end of a number that includes a decimal point. Zeros at the end of a number without a decimal point are ambiguous. We will assume they are NOT significant. Practice assigning significant figures.

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