Sample-size estimation

• An appropriate sample size should be computed when the study is being designed and the statistical method of computation reported.
• Statistical methods that take into account multiple evaluations of the data should be used when an interim evaluation is carried out.

Data handling

• Rules for stopping data collection should be defined in advance.
• Criteria for inclusion and exclusion of data should be established prospectively.
• Criteria for defining and handling outliers should be decided when the experiment is being designed, and any data removed before analysis should be reported.
• The primary end point should be prospectively selected. If multiple end points are to be assessed, then appropriate statistical corrections should be applied.
• Investigators should report on data missing because of attrition or exclusion.
• Pseudoreplication issues need to be considered during study design and analysis.
• Investigators should report how often a particular experiment was performed and whether results were substantiated by repetition under a range of conditions.

Recommendations adapted from Landis et al. (2012).¹⁶ Both images: © Jim Frazier