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Accuracy and Precision Measurements are qualitative or quantitative. –Qualitative measurements give results that are descriptive and non-numerical. Example:

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Presentation on theme: "Accuracy and Precision Measurements are qualitative or quantitative. –Qualitative measurements give results that are descriptive and non-numerical. Example:"— Presentation transcript:

1 Accuracy and Precision Measurements are qualitative or quantitative. –Qualitative measurements give results that are descriptive and non-numerical. Example: –Quantitative measurements give results that are definite, usually as numbers and units. Example:

2 Accuracy and Precision Measurements work best when they are accurate and precise –Accuracy is a measure of how close a measurement comes to the actual or true value of whatever is measured. To evaluate the accuracy of a measurement, it must be compared to the correct value. –Precision is a measure of how close a series of measurements are to one another. The precision of a measurement depends on more than one measurement.

3 Accuracy and Precision

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5 In this picture, all of the darts land on the bulls- eye which illustrates good precision and accuracy. In this picture, all of the darts land near each other, but away from the bulls-eye which illustrates good precision, but poor accuracy.

6 Accuracy and Precision Here the darts are not close to each other, but are close to the bulls-eye indicating poor precision, but good accuracy. Finally, the darts are not close to each other or near the bulls-eye indicating both poor accuracy and poor precision.

7 Accuracy and Precision Sometimes there is a difference between the accepted value and the experimental value. This difference is known as error. Error = accepted value – experimental value –Error can be positive or negative depending on whether the experimental value is greater than or less than the accepted value.

8 Accuracy and Precision Often it is useful to calculate relative error, or percent error. Percent error = error x 100% accepted value –The percent error will always be a positive value.


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