Suppose I have a set of 5,000 proposals submitted to a competition for funds. After review 10% were Rated Highly, 15% Average, 75% Poor.
I want to take a sample from the group of proposals and test them for plagiarism.
How many should I select from the 5000? How many from each of the 3 groups (high, average, poor)? Couldn't I just do a simple power calculation and draw that many from the pool at random, or select the required sample size such that 10% are rated high, 15% average, and 75% poor? Suppose 95% confidence interval with 5% margin of error.
Does it matter if plagiarism is abundant 25%, or scarce 2%, in my population?