Email updates

Keep up to date with the latest news and content from BMC Musculoskeletal Disorders and BioMed Central.

Open Access Highly Accessed Study protocol

Early intervention for adolescents with Patellofemoral Pain Syndrome - a pragmatic cluster randomised controlled trial

Michael S Rathleff*, Ewa M Roos, Jens L Olesen and Sten Rasmussen

  • * Corresponding author: Michael S Rathleff

BMC Musculoskeletal Disorders 2012, 13:9  doi:10.1186/1471-2474-13-9

PubMed Commons is an experimental system of commenting on PubMed abstracts, introduced in October 2013. Comments are displayed on the abstract page, but during the initial closed pilot, only registered users can read or post comments. Any researcher who is listed as an author of an article indexed by PubMed is entitled to participate in the pilot. If you would like to participate and need an invitation, please email, giving the PubMed ID of an article on which you are an author. For more information, see the PubMed Commons FAQ.

Wrong power calculation and analysis

David J Torgerson   (2012-03-01 15:32)  York University email

You are doing a cluster randomised controlled trial. However, your sample size is incorrect: you have not adjusted for clustering. Also your analysis strategy is incorrect: again you need to adjust for clustering. Even if you did the adjustment you only have 4 clusters, which is insufficient cluster replication. You need to increase the number of clusters to at least 8 and recalculate your sample size.

Competing interests



Post a comment