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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 misr@rn.dk

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

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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

None

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