A well-designed experiment should provide robust and unbiased results. Scientific rigor, as defined by the NIH, is the strict application of the scientific method to ensure robust and unbiased experimental design, methodology, analysis, interpretation and reporting of results.
These resources are to aid in the planning of a rigorous experimental design and are not meant to replace or provide rules as to how experiments should be conducted. They are merely guidance to aid in the experimental planning process. More resources on reproducibility are available on the reproducibility by topic webpage.