Error Analysis

Error

Error is the difference between the actual value of a quantity and the value obtained in measurement.

Systematic Error

Systematic errors are errors which tend to shift all measurements in a systematic way so their mean value is displaced. Systematic errors can be compensated if the errors are known.

Sources of Systematic Error

1. zero error, which cause by an incorrect position of the zero point,
2. an incorrect calibration of the measuring instrument.
3. consistently improper use of equipment.

Steps to reduce Systematic Error

1. Conducting the experiment with care.
2. Repeating the experiment by using different instruments.

Zero Error

1. A zero error arises when the measuring instrument does not start from exactly zero.
2. Zero errors are consistently present in every reading of a measurement.
3. The zero error can be positive or negative.

Random Error

1. Random errors arise from unknown and unpredictable variations in condition.
2. It changes from one measurement to the next.

Causes of Random Error

Random errors are caused by factors that are beyond the control of the observers. Random error can cause by:

1. personal errors such as human limitations of sight and touch.
2. lack of sensitivity of the instrument: the instrument fail to respond to the small change.
3. natural errors such as changes in temperature or wind, while the experiment is in progress.
4. wrong technique of measurement.

How to avoid random error

1. Taking repeat readings
2. Find the average value of the reading.

Parallax Error

A parallax error is an error in reading an instrument due to the eye of the observer and pointer are not in a line perpendicular to the plane of the scale.