# The Science of Physics Section 1-2 Accuracy vs. Precision.

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The Science of Physics Section 1-2 Accuracy vs. Precision

Accuracy Accuracy is the agreement of a measurement with the accepted value. “Error” is usually associated with accuracy. – Human error – Method error – Instrument error Errors can often be corrected.

Precision Precision of a measurement tells how close several measurements of the same quantity are to each other. Precision also deals with how exact a measurement can be. Uncertainty is usually associated with precision. Example: – A metric stick marked off with smallest units of cm is less precise than one marked off in mm.

Example 1 Data Set A: 0.8888 g 0.9959 g 1.1182 g 1.0033 g 0.9938 g 1.0000 g--average Data Set B: 1.3110 g 1.3109 g 1.3111 g 1.3110 g 1.3110 g--average Actual Mass: 1.0000g Good/poor accuracy? Good/poor precision?

Example 1 Data Set A: 0.8888 g 0.9959 g 1.1182 g 1.0033 g 0.9938 g 1.0000 g--average Data Set B: 1.3110 g 1.3109 g 1.3111 g 1.3110 g 1.3110 g--average Actual Mass: 1.0000g Good/poor accuracy? Good/poor precision?

Example 2 In this example there are 2 sets of data for the 5 measurements of the length of a stick. Which set of data is more precise? Data Set A: 1.1 m 1.2 m 1.1 m 1.2 m Data Set B: 1.12 m 1.11 m 1.10 m 1.13 m

Example 2 The range of measurements for data set A is 0.1 m. The range of measurements for data set B is 0.03 m. Thus data set B is more precise. Data Set A: 1.1 m 1.2 m 1.1 m 1.2 m Data Set B: 1.12 m 1.11 m 1.10 m 1.13 m