Imagining the following situation where A/B are independent results:
- A is a 51% result, given N datapoints
- B is a 50% result, given M datapoints
how many data points (ie N and M) do you need to have confidence that the difference between A/B is statistically significant?
Best Answer
There are various sample size calculators you can use online and in various software for a two-sample proportions test.
Here's the calculation using Stata that suggests that you would need N=M=39,240 for a two-sided alternative test at conventional levels: