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Accuracy & Precision in Measurement

Accuracy & Precision in Measurement. Also Qualitative vs Quantitative Data. Accuracy: How close you are to the actual value Depends on the person measuring Calculated by the formula: % Error = (YV – AV) x 100 ÷ AV Where: YV is YOUR measured Value & AV is the Accepted Value. Precision:

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Accuracy & Precision in Measurement

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  1. Accuracy & Precisionin Measurement Also Qualitative vs Quantitative Data

  2. Accuracy: How close you are to the actual value Depends on the person measuring Calculated by the formula: % Error = (YV – AV) x 100 ÷ AV Where: YV is YOUR measured Value&AV is the Accepted Value Precision: How finely tuned your measurements are or how close they can be to each other Depends on the measuring tool Determined by the number of significant digits Accuracy & Precision

  3. Accuracy & Precision • Accuracy & Precision may be demonstrated by shooting at a target. • Accuracy is represented by hitting the bulls eye (the accepted value) • Precision is represented by a tight grouping of shots (they are finely tuned)

  4. Accuracy without Precision Accuracy & Precision No Precision & No Accuracy Precision without Accuracy

  5. Accuracy - Calculating % Error • If a student measured the room width at 8.46 m and the accepted value was 9.45 m what was their accuracy? • Using the formula:% error = (YV – AV) x 100 ÷ AV • Where YV is the student’s measured value & AV is the accepted value

  6. Accuracy - Calculating % Error • Since YV = 8.46 m, AV = 9.45 m • % Error = (8.46 m – 9.45 m) x 100 ÷9.45 m • = -0.99 m x 100 ÷ 9.45 m • = -99 m÷9.45 m • = -10.5 % • Note that the meter unit cancels during the division & the unit is %. The (-) shows that YV was low • The student was off by almost 11% & must remeasure • Acceptable % error is within 5%

  7. Acceptable error is +/- 5% • Values from –5% up to 5% are acceptable • Values less than –5% or greater than 5% must be remeasured remeasure -5% 5% remeasure

  8. Data • Data is information gathered during experiences (whether it’s when you walk into a room or during an experiment, we are constantly gathering data.) • Data is either qualitative or quantitative.

  9. Quantitative Data • Measurements (uses numbers and units) • Not descriptive

  10. Qualitative Data • Descriptive information taken (such as color, taste, or personal opinion) – uses words • NOT measurements

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