Introduction to Sample Size Calculation
Training session with Dr Helen Brown, Senior Statistician, at The Roslin Institute, January 2016.
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These training sessions were given to staff and research students at the Roslin Institute. The material is also used for the Animal Biosciences MSc course taught at the Institute.
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A spreadsheet to carry out the calculations described in the presentation may be copied here: http://datashare.is.ed.ac.uk/handle/10283/1996
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*Recommended YouTube playback settings for the best viewing experience: 1080p HD
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Content:
Example: How many mice to test effect of Chloram on red blood cell count?
New study requires
10 mice per group, ie 20 mice in total
If 3 groups then: 3x10 = 30 mice would be required
Typical statement in a proposal or protocol might read:
‘With a sample size of 10 mice per treatment group, and a true mean difference in red blood cell count of 0.50, there is 80% power to detect a obtain a statistically significant difference between treatment groups at the 5% significance level.’
Supposing only 12 mice are available (6 per group)
