RPI and CTP:
Using Statistics for better Search
Matthew Henry, Portent Interactive, Seattle, WA
Edited by Ian Lurie
September 22, 2004
A note from Ian: Search Engine Optimization may seem more art
than science. And it definitely requires a bit of both. But you can
use some basic statistics to focus your campaigns, separate
reasonable goals from unreasonable ones, and more efficiently use
your search marketing dollars.
Matthew Henry is Portent Interactive's resident search engine
optimization genius and math wizard. Read on to learn how two of his
creations - Relative Position Index and Click-Through Prediction -
help target our SEO campaigns.
RPI: Your Search Engine Optimization Potential
RPI, or Relative Position Index, is a metric we use to track search
engine optimization potential and progress. Your RPI score shows how
well you're doing relative to your competitors - it's an indicator
of how you're doing at outranking them. It is based on a logarithmic
scale, so an increase of 1 to this value translates into a tenfold
increase in ranking strength.
The formula for RPI is:
is the number of competing sites in a search for this term.
rank is the rank that your site gets on a search for the
case you're not a math geek, here's another way to look at it:
An RPI of 0 means you rank dead last.
An RPI of 1 means you rank in the top 10%.
An RPI of 2 means you rank in the top 1%.
An RPI of 3 means you rank in the top 0.1%.
An RPI of 4 means you rank in the top 0.01%.
An RPI of 5 means you rank in the top 0.001%.
and so on...
do we need RPI? Because it's a good way to judge good search engine
optimization targets. For any two keyphrases, doing the same amount
of work will get you roughly the same RPI, but the actual ranks may
be quite different. So we can use RPI to figure out which terms will
get you the highest rank, the fastest, for the same amount of work.
This makes RPI an essential strategic tool - we can figure out which
shorter-term 'money' terms will get you a quick burst of traffic,
and plan our longer-term campaign for higher-profile, more
competitive terms that will require more work but also offer a
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