These are great project resources to review whether you are writing a grant or not. But first, a note about Sample size calculation.
Sample size calculation
If a sample size estimation is needed, we will need the following information: (It’s okay if the only information available is an “educated guess”)
1). Outcome Variable Type:
- For a continuous variable (such as height or weight), we need: (bring in relevant literature)
- The average value and the standard deviation of the control group;
- For a dichotomous variable (such as: yes/no response), we need:
- The average proportion of the control group or the population
2). The estimated difference between the control and the treatment you would like to detect (effect size).
Both of these are often derived from similar studies that are in the literature AND/OR through pilot studies.
Resources
Excellent introduction to the statistical concepts in power calculations for sample sizes. Also discusses commercially available Sample Size Software. 2:Kwansky MJ Statistical Power and Sample Size: what you need and how much. https://www.feinberg.northwestern.edu/sites/bcc/docs/2016lectures/StatisticalPowerSampleSize.pdf
For information on power calculations for specific statistical methods see Section D of St. George’s guide https://www-users.york.ac.uk/~mb55/guide/guide14.pdf OR to navigate online https://www-users.york.ac.uk/~mb55/guide/guide.htm
The Sample Size Shop created by the University of Florida calculates sample size when provided a study design with normal distribution outcomes. It is calculated by GLIMPSE, a statistical software program provided by the university. It is used to determine the power and sample sizes for many statistical tests. GLIMPSE provides a Guided Study Design template, Matrix Study Design template, and the opportunity to Upload a Study Design. GLIMPSE also includes calculations for confidence intervals and creates basic power curves. |
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Please use the following text to acknowledge the CTSI Study Design and Biostatistics Center:
"This investigation was supported by Translational Research: Implementation, Analysis and Design (TRIAD), with funding in part from the National Center for Advancing Translational Sciences of the National Institutes of Health under Award Number UM1TR004409. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health."
"This investigation was supported by the Study Design and Biostatistics Center (SDBC), with funding in part from the National Center for Advancing Translational Sciences of the National Institutes of Health under Award Number UM1TR004409. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health."