Below we provide resources on how to prepare data for statistical analysis (Data Preparation), freely available software for conducting statistical analyses (Statistical Analysis Software), tutorials on and links to on-line calculators for conducting power and sample size calculations (Power and Sample Size Calculations) and links to statistics educational resources appropriate for clinicians (Educational Resources).
A clean, suitably-structured, and well-documented data set is critical for efficient and accurate statistical analysis. Most commonly, data is imported into statistical analysis programs as a comma delimited text file. For easy and accurate importation of data into statistical software, it is essential that the data adhere to a regular structure with consistent entries.
While it is not required, using REDCap (Research Electronic Data Capture) can greatly simplify data collection and minimize costly and time-consuming data clean-up activities. REDCap is a secure web-based application for building and managing online databases for research and is supported by the Clinical and Translational Science Center Biomedical Informatics team.
Regardless of the software used to record data, to facilitate importation into statistical software, the data must have a consistent format.
Guidance on how to format data is provided in the following resources:
In addition, every data set must include a data dictionary that describes each variable and identifies acceptable values. Additional information on data dictionaries is available on the UC Davis REDCap website.
Note: SPSS, SAS, and JMP can be obtained at a reasonable cost through UC Davis Information and Educational Technology.
A sufficient sample size is necessary for every study to ensure adequate power for detecting clinically meaningful differences. Excellent resources explaining the concepts of power and sample size and what they depend on are available at Biostats4You: Power and Sample Size Concepts.
These guides provide illustrated examples of how to estimate sample size requirements for the indicated statistical procedure using freely available software.
This website provides online tools to estimate the sample size needed for the following clinical trial settings, specifically superiority, equivalence, and non-inferiority trials for binary or continuous outcomes.