[Zope] statistics-n-nnn tags

[Kent Polk]

 From the DTML manual  :

variance-nnn : The variance of numeric values computed with a
degrees of freedom equal to the (count - 1).

variance-n-nnn  :  The variance of numeric values computed with a
degrees of freedom equal to the count.

standard-deviation-nnn  :  The standard deviation of numeric values
computed with a degrees of freedom equal to the (count - 1).

standard-deviation-n-nnn :  The standard deviation of numeric values
computed with a degrees of freedom equal to the count.

So I try:
 <!--#var standard-deviation-EGO -->
which works, however, 
 <!--#var standard-deviation-2-EGO -->

provides:

Traceback (innermost last):
  File "<stdin>", line 1, in ?
  File "pedsys.py", line 218, in summary
    return HTML(html)(self)
  File "./DT_String.py", line 513, in __call__
  File "/usr/pkg/zope/lib/python/DocumentTemplate/DT_In.py", line 678,
      in renderwob
    try: append(render(section, md))
KeyError: standard-deviation-2-EGO

All statistics-n-nnn forms result in a key error regardless of how/
where I use them. Am I misreading the manual on how to use them?

I'm running Zope 1.10.2  but I peeked at 1.11.0pr1 and saw that
there have been no changes to DT_InSV.py between the two versions
(1.10.2 and 1.11.0pr1).

Thanks
Kent