[O] calculation question

[Jude DaShiell]

When an org table like:
|---| time stamp | systalic | diastalic | pulse |
|-
| # | [2011-07-13 Wed 04:15] | 134 | 89 | 80 |

gets used and I want to calculate averages for systalic and diastalic and 
do that in the #+TBLFM: line do I use $2 and $3 for systalic and diastalic 
or do I use $3 and $4 because of the marker column?