TABLE OF CONTENTS In the last chapter, we discussed accuracy and how it is stated in terms of the difference between the true value and the measured value. This difference is called error. This chapter discusses methods for anticipating and correcting for error in measurement. This is done by applying statistical techniques and by using computer-generated calibration curves that are either manually or automatically applied. You should be familiar with the concepts found in this chapter in order to make measurements with any degree of confidence that the required accuracy will be achieved. Remember: all measurements have some error.
There are three major sources of measurement error: gross, systematic, and random.
Gross error is people-caused error. Causes of people error are as diverse as people are, but some of the major causes are:
Using the wrong meter for the application.
Using the wrong scale for the measurement.
Interpolating a reading incorrectly.
Committing a zero error, such as failing to accurately align the zero point of the ruler with the beginning line point (this is the same as aligning the zero incorrectly for any measurement).
Making a parallax error by reading the marks at any angle other than directly overhead.
Misreading numerals.
Although there are many more causes of such "people errors," these will give you an idea of what gross error is all about.
The types of measurement error that occur once gross error has been ruled out are either systematic errors or random errors.
Systematic error is...
