
(a)  The sample mean


(b)  The sample variance (for $n\ge 2$)


(c)  The sample autocorrelation coefficients of lags $k=1,2,\dots ,K$, where $K$ is a userspecified maximum lag, and $K<n$, $n>1$.
The coefficient of lag $k$ is defined as


(d)  A test statistic defined as
If $n$ is large and $K$ is much smaller than $n$, STAT has a ${\chi}_{K}^{2}$ distribution under the hypothesis of a zero autocorrelation function. Values of STAT in the upper tail of the distribution provide evidence against the hypothesis; G01ECF can be used to compute the tail probability.
Section 8.2.2 of Box and Jenkins (1976) provides further details of the use of STAT. 
On entry,  ${\mathbf{NX}}\le {\mathbf{NK}}$, 
or  ${\mathbf{NX}}\le 1$, 
or  ${\mathbf{NK}}\le 0$. 