Randomisation, blinded outcome assessment, and sample size calculation in systematic reviews of animal studies.

a<p>Summarises the data of six systematic reviews of treatment strategies for acute ischemic stroke. There is an overlap of 18 publications between references <a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.1000245#pmed.1000245-Sena1" target="_blank">[16]</a> and <a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.1000245#pmed.1000245-VanderWorp2" target="_blank">[19]</a>.</p><p>ALS, amyotrophic lateral sclerosis; N/A, data not available; RDS, respiratory distress syndrome.</p

Four types of bias threatening internal validity.

<p>Adapted from <a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.1000245#pmed.1000245-Juni1" target="_blank">[12]</a>,<a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.1000245#pmed.1000245-Altman1" target="_blank">[13]</a>.</p