CBSE Class 11-science Answered

Systematic error is the error that is constant in a series of repetitions of the same experiment or observation. Usually, systematic error is defined as the expected valueof the overall error.

Systematic errors can be either constant, or be related (e.g. proportional or a percentage) to the actual value of the measured quantity, or even to the value of a different quantity (the reading of a ruler can be affected by environment temperature). 

Constant systematic errors are very difficult to deal with, because their effects are only observable if they can be removed. Such errors cannot be removed by repeating measurements or averaging large numbers of results. A common method to remove systematic error is through calibration of the measurement instrument.

Random Error is the fluctuating part of the overall error that varies from measurement to measurement. Normally, the random error is defined as the deviation of the total error from its mean value.

An example of random error is putting the same weight on an electronic scales several times and obtaining readings that vary in random fashion from one reading to the next. The differences between these readings and the actual weight correspond to the random error of the scale measurements.

In contrast to systematic errors, the effect of the random errors may be reduced by repetition of the experiment or observation and averaging the outcomes.