https://www.students4bestevidence.net/sample-size-a-practical-introduction/
Sample Size:
Important component of planning stage – there are methods available to estimate sample sizes before conducting a study, so that there is a good chance of obtaining a statistically significant result. Study needs to be large enough to ensure that the results are generalisable, but not so large that the research resources are wasted.
Sample size is a judgement issue based on what is considered a clinically important difference between groups.
If too small:
• type 1 or type 2 errors
• power inadequate to show how significant and clinically important difference is
• unethical
If too large:
• small differences found that are not clinically important
• waste of resources
• unethical
Sample Size Calculations:
Several formula are available for sample size calculations, but information is needed on four variables are needed:
• Size of response to control intervention
• Expected size of response to experimental intervention
• Significance level (arbitrary determination; usually set at 0.05 by convention; risk of committing a type 1 error)
• Power (probability of rejecting null hypothesis; probability of a type 2 error is beta, so power is defined as 1-beta; by convention it is set at 0.80.
We have not yet got to this page to finish it yet. We will eventually. Please contact us if you have something to contribute to it or sign up for our newsletter or like us on Facebook and Instagram or follow us on Twitter. |
Page last updated:
Comments are closed.