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Error, Accuracy, Deviation, and Precision in Lab data

Error, Accuracy, Deviation, and Precision in Lab data. Common misconception :. Any mistake in a lab is considered Error? NOT TRUE , lab Error does NOT include calculating wrong, measuring wrong, etc…. TYPES OF ERRORS: Systematic & Random. Systematic Error

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Error, Accuracy, Deviation, and Precision in Lab data

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  1. Error, Accuracy, Deviation, and Precisionin Lab data

  2. Common misconception: • Any mistake in a lab is considered Error? • NOT TRUE, lab Error does NOT include calculating wrong, measuring wrong, etc…

  3. TYPES OF ERRORS: Systematic & Random • Systematic Error • Produces an error that is always the same. Either always high or always low.

  4. TYPES OF SYSTEMATIC ERROR • INSTRUMENTAL ERROR • caused by faulty inaccurate equipment, use in labs • PERSONAL ERROR • caused by some peculiarity or bias of the observer—notacceptable in labs, these are “mistakes” • EXTERNAL ERROR • caused by external conditions, use in labs if applicable

  5. TYPES OF ERRORS • RANDOM ERROR: • Errors that are due solely to chance. They will produce errors that are both above and below the accepted value. • Random errors cannot be corrected but can be minimized by doing a large number of observations • Random error always is present

  6. ACCURACY • The closeness of a measurement to the accepted value for a specific physical quantity

  7. ACCURACY is represented MATHEMATICALLY as ERROR (Relative) or % Difference Mean Experimental Value Absolute Error Accepted Value Absolute Error Relative Error Accepted Value

  8. Percent Difference (%Diff) • When comparing twovalues or sets of Data to determine error between them, the calculation is called percent difference First calculate the average if using sets of data

  9. PRECISION • The agreement of several measures that have been made in the same way with each other • It is also how exact an instrument can measure

  10. PRECISION is represented MATHEMATICALLY as DEVIATION (Relative) Each Observed Experimental Value Absolute Deviation done for each measurement Mean Experimental Value Average Absolute Deviation Relative Deviation Mean Experimental Value

  11. Example: Deviation and Error

  12. 8.93 m/sec 9.36 m/sec 10.48 m/sec 9.15 m/sec 9.33 m/sec 47.25 m/sec Absolute and Relative Error First: CALCULATE THE AVERAGE

  13. ABSOLUTE ERROR RELATIVE ERROR

  14. Absolute Deviations Absolute and Relative Deviation

  15. 0.52 m/s 0.09 m/s 1.03 m/s 0.30 m/s 0.12 m/s 2.06 m/s Absolute and Relative Deviation AVERAGE ABSOLUTE DEVIATION DA

  16. Relative Deviation

  17. Explain the difference between: Accuracy and Precision Aka Error and Deviation You should be able to: In a lab, be able to calculate Error % or % Difference and Deviation % when needed.

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