Submitted by: Submitted by jam135
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Words: 500
Pages: 2
Category: Business and Industry
Date Submitted: 06/05/2014 10:46 AM
Theory of Error
1.0 DEFINITIONS
1.1 ERROR
This word is used to denote the difference between a measured value and a "true" value. It is also used to indicate the degree of- uncertainty by expressing it in quantities as standard deviation, probable error, etc...
1.2 DISCREPANCY
This is the difference between two measured values such as between two students or between the student's reading and the published value.
2.0 CLASSIFICATION OF ERRORS
2.1 SYSTEMATIC ERRORS
2.1.1 ERRORS OF CALIBRATION OF INSTRUMENTS
2.1.2 PERSONAL ERRORS
An example of this would be parallax errors caused by the observer always holding his head to one side of an indicating needle.
2.1.3 EXPERIMENTAL CONDITIONS
If an instrument is calibrated under one set of conditions but is used under another set of conditions, the readings will be wrong.
2.1.4 IMPERFECT TECHNIQUE
An example would be where a flow reading is being made by timing the flow of liquid into a graduated cylinder and a small amount splashes out.
2.2 RANDOM ERRORS
2.2.1 ERRORS OF JUDGEMENT
For example, when a needle is between two mark's then it will be a judgment call as to whether the reading should be .7 or .8, for example.
2.2.2 ERRORS CAUSED BY FLUCTUATING CONDITIONS
An example would be in taking amperage readings when the line voltage is fluctuating.
2.2.3 SMALL DISTURBANCES
For example, trying to weigh something when nearby machinery is causing vibrations. The Injection Blow Molding machine is very sensitive to temperature changes. If the door is opened and closed quickly or the forced air furnace comes on, it will have a small effect on the process.
2.2.4 DEFINITION
For example, the lack of good definition of a boundary will make it difficult to get consistent readings. An irregular edge of a table will make it difficult to measure the width of the table.
2.3 ILLEGITIMATE ERRORS
Most...