Term Weight & Glasgow Weight vs. Keyword Density
The author's views are entirely their own (excluding the unlikely event of hypnosis) and may not always reflect the views of Moz.
For search engines, keyword density has long been held to be a reliable measure of the concentration of a particular keyword or phrase on a specific page. However, this method of mesurement has long been known in the scientific community to be a poor representation and poor methodology for discovering the 'weight' a particular page has for a term.
Alternatively, IR developers (search engineers) have proposed and used a system called 'term weight' and variations thereof (normalized term weight, Glasgow weight, etc.).
Classic Normalized Term Weight uses the following equation:
Wi = tfdi / max tfdi * log (D/dfi)
Where:
tfdi = term (or phrase of a given length) frequency in document
tfdi = maximum frequency of any (same number word) phrase in document
D = number of documents in the database (when using Google, I estimate at 8.1 billion)
dfi = number of documents containing the term/phrase (# of results for a search in quotes)
A second equation, Glasgow Weight, can also be useful (I generally use both when analyzing my own site vs. the competition):
Wij = log(freqij + 1) / log(lengthj) * log (N/ni)
Where:
freqij = frequency of term i (a word or phrase of a given length) in document j
lengthj = number of unique terms (word or phrase of the same length) in document j
N = number of documents in database (again, I use 8.1 billion for Google)
ni - number of documents containing the term (results of a search in quotes)
Using these equations and the resulting numbers for comparison is a much better way to check your page's use of a specific keyword phrase or term than just measuring keyword density. I hope to have an SEOmoz tool up in the next 2 months that can help by making the calculations for you - in the meantime, use Excel.
Comments
Please keep your comments TAGFEE by following the community etiquette
Comments are closed. Got a burning question? Head to our Q&A section to start a new conversation.