How Accurate are IR Usage Statistics?

Experiment: simple random sample of 2 years of download data (n=341, N=3.3 million for 96.20% certainty), manually checked to determine if robot or human. DSpace 1.8.2 with U. Minho DSpace Statistics Add-on v. 4. Apache Tomcat behind Apache HTTP server; logs in Apache Combined Log Format. Minho registers every download in the PostgreSQL database. Results to be published in July 2016 issue of Library Hi Tech (Greene 2016). This dataset is used to experimentally test different detection techniques used alone and in combination, and different out-of-box techniques used by the major repository platforms DSpace and EPrints. 85% of unfiltered repository downloads come from robots.