Indeterminate or random errors arise from several uncontrollable variables in successive measurements. Since these errors can neither be predicted nor estimated, they are never eliminated. Sometimes it is difficult even to identify the individual error sources. Consider an example of random errors from the electrical noise in an instrument. The fluctuations can go in both positive and negative directions and differ in magnitude. Due to these random variations, the indeterminate errors are scattered. However, for a large data set, the mathematical laws of probability help to find the most probable results in the mean or median. On plotting the data with random errors, the values distribute in both directions around the most frequently occurring central value. The frequency of occurrence goes down gradually as the values go higher and lower from the central value. Such a distribution plot is known as the Gaussian curve.