Scatter and Confidence Interval

The Student t-factor depends on the statistical reliability P and the number of degrees of freedom/= n - 1. Because a certain statistical reliability P must be chosen for the calculation of T, which has to be taken into account when interpreting the result, the result is given in % P  

In contrast to the scatter range T of individual values, the scatter range of the arithmetic mean value is denoted as confidence interval T/Jn. 

If a series of m arithmetic mean values Pi is determined each from n individual measurements, the following relation results for the estimated value of the standard deviation of the arithmetic mean values  

The statistical reliability of a result is expressed by the scatter range T and the confidence interval. The confidence interval means that P% of all individual measurements, whose mean value x is stated as a result, can be expected to be within the range x+T and x—T. Using details about T, one judges the quality 

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