When I first looked at Matt Inman and Rand Fishkin’s Page Strength tool just after its launch the correlation coefficient with PageRank was extremely high at 0.92 on a random sample of 26 urls (see Page Strength). Now the Aviva Directory has published a list of Bob Mutch’s directories showing their Page Strength and simply by adding the current PageRank value to the table it is possible to calculate a correlation coefficient on this larger data set.
Directories with a current PageRank of zero were removed from the table so as not to perturbate the results. Many of them are PageRank zero because they are banned from Google’s index, for example galaxy.com (Page Strength 5), cannylink.com (Page Strength 4), dirone.com (Page Strength 3.5) and so on.
After the removal of all directories with a current PageRank of zero the remaining 277 were plotted on an x,y chart and the correlation coefficient calculated. The results were as follows:

The correlation coefficient was lower than in the previous data set at 0.78 but still significant. I had a quick look at some of the outliers like topicalbeach.com with a PageRank of 5 and a Page Strength of 1.5 and found that in this case Aviva Directory had misreported the Page Strength which is actually 4.5. Validating the data would increase the correlation coefficient.
Users of the Page Strength tool have reported a variety of anomalies because the Yahoo search operator linkdomain:domain.tld used by the tool does not always return correct results. Sorry Matt and Rand but I cannot see this tool as anything other than a very unreliable proxy for the already unreliable PageRank metric.


Page Strength Revisited - Read More...