Use these free online calculators to estimate the needed sample size for a straightforward one- or two-group study. The methods referenced in these…
These resources explain the concepts of power and sample size and what they depend on.
These resources provide guidance on how to find and work with a biostatistician.  
These resources provide guidance on collecting and managing study data.  
These resources explain the concepts involved in carrying out hypothesis tests and correctly interpreting the resulting p-values.  
These resources explain the key concepts involved in designing, evaluating and interpreting the results of diagnostic tests: sensitivity, specificity…
These resources explain what multiple testing is, why it is problematic, and how to recognize and control for it.
These resources describe commonly used non-parametric methods and their advantages and disadvantages.
These resources explain what post-hoc power analyses are and why they aren’t useful in most cases.