When the number of measurements of a quantity is particularly small and statistical
analysis of the distribution of error values is required, problems can arise when using
standard Gaussian tables in terms of z as defined in equation (3.16) because the mean of
only a small number of measurements may deviate significantly from the true measurement
value. In response to this, an alternative distribution function called the Student-t
distribution can be used which gives a more accurate prediction of the error distribution
when the number of samples is small. This is discussed more fully in Miller (1990).