According to Barker, Pistrang and Elliot (2010, p 62) reliability refers to the degree of reproduce ability measurement. A variety of different statistics are used to measure reliability. For some reason confusion continues to surround their use and selection. The first step is to set up which measurement scale is involved since this determines the reliability statistics. For practical needs only interval and nominal scales required to be assumed. Ordinary scales are analyzed as if they were interval scales. The methods used to quantify reliability are the statistics and probability mathematics. Reliability statistics can be widely categorized into the discrete functions treatment, point processes and continuous functions. Reliability is based on two state discrete systems since the component is in either in a failed or operational state. Continuous functions describe those situations which are ruled by a continuous variable such as distance or time travelled. The variations between continuous and discrete functions are one of how the problem is treated and not necessarily of the mechanics or physics of the situation. One of the most common reliability statistics is the reliability coefficient which is an index that takes on value from 0.0 to 1.0. A reliability coefficient of 0.0 denotes that the scores are wholly undependable whereas the 1.0 coefficient denotes that the scores are wholly dependable.