Public Library Blogs: A few metrics

Public Library Blogs: 252 Examples demonstrates again what appears to be true of any group of blogs: There is no such thing as an average blog–and they vary so much that the mean and median for any given measure tend to be very different.

So it is with these 252 blogs. Here, then, the metrics I used (all based on posts during March, April and May 2007), with the mean (the average of all blogs), the median (the point at which half the blogs have a higher number and half have a lower), and the limit for “outliers”–most commonly the top quintile for a given measure (that is, the top 20%). The book lists the outliers for each measure. Within the descriptions that make up the bulk of the book (of which metrics are a tiny part), metrics always appear–and they’re boldfaced (or, in one special case, italicized) if they’re outliers.

  • Frequency (number of posts): The mean is 23.7 posts, roughly two per week–but the median is 12.0 posts, slightly less than one per week. The top 20% have 33 or more posts during the 92-day quarter. (If you’re wondering, 10 average at least a post a day.)
  • Comments: The mean is 4.5 comments–but the median is zero, since only 118 of the blogs had any comments at all, and 25 of those had one comment each during the quarter. Quite a few of them don’t allow comments, generally for sensible reasons. (Note: I eliminated obvious groups of spam comments from the counts–and no, I didn’t consider teens dissing one another as spam). The top 20% have five or more comments during the three-month period.
  • Comments per post: You already know the median (zero); the mean is 0.3, with only 45 blogs exceeding that modest figure. I listed the 41 blogs (16%) averaging at least half a comment per post; fourteen averaged at least one comment per post.
  • Illustrations: Average 18.6 during the quarter, median 5.0; top 20% start at 24 illustrations.
  • Illustrations per post: Average 0.7 per post, median 0.5 per post. Too many blogs have essentially 1.0 illustrations per post (book review blogs, etc.) to use a boundary at the 20% mark, but I list the 44 blogs (17%) with at least 1.1 illustrations per blog.
  • Total length: The whole set of blogs totaled just over a million words for the three-month period; the average blog had 4,120 words, but the median was 1,968 words. The outliers in this case are slightly more than 20%; I used 5,000 words as a reasonable cutoff.
  • Average length per post: The “average average” was 187.3 words–roughly two typical paragraphs. The median was 153.8 words. In this case, I noted two outlying groups–those with longish posts (I used 251 words per post as the cutoff, roughly the top 20%) and those with considerably shorter-than-average posts (I used 89 words per post as the cutoff).
  • Longevity: I didn’t attempt to calculate a mean or median, and blogs had to be around for at least six months to qualify. (I did not remove blogs that had no posts between June 1 and the completion of the study. Summer can be strange at some libraries.) Of the 252 blogs, 155 began during 2006 and another 38 began in the last half of 2005. I list the other 59, the 23% that had been around at least two years by the time of the study.

The mythical “average public library blog,” then, began in early 2006 and had 24 posts with five comments, 19 illustrations and a total of around 4,000 words or around 180 words per post. For what that’s worth.

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