# Krippendorffs alpha

#### Verbro

##### New Member
I am planning to do a reliability study in which I want to test the inter-rater reliability of an histopathological grading scheme (several pathologists grade a set of biopsies under the microscope). The grading scheme has 5 categories on an ordinal scale. There will be multiple raters. I am planning to use Krippendorffs alpha as a reliability measure.
I have 2 questions related to this:
• Is there any way to perform a sample size calculation?
• In which way is the result influenced by the number of cases in each category? As some of the categories in my grading scheme are rare, there is a risk that these categories will not be represented in a random sample (or very small in numbers in a proportionate sample). Is it an option to create a sample with even distribution of all categories?