Yep, my read too. The code he provides is definitely the Clopper-Pearson formula. [1] This confused me as well, since I've always used the normal central-limit

Yep, my read too. The code he provides is definitely the Clopper-Pearson formula. [1] This confused me as well, since I've always used the normal central-limit-based confidence interval for binary outcomes. [1] https://en.wikipedia.org/wiki/Binomial_proportion_confidence_interval#Clopper%E2%80%93Pearson_interval https://en.wikipedia.org/wiki/Binomial_proportion_confidence... (I am no expert in the analytic underpinnings of the beta distribution or precisely how it is the conjugate prior to the binomial -- or, rigorously speaking, what conjugate prior means -- but the formula here lines up with his formula :P )