I'm running thru the UWorld biostats right now. I don't really think it's that good tbh. It's basically just 3-5 questions per biostats topic (about 20 topics total) = 73 total questions. You do a set of 3-5 questions and then they give you like 3-4 paragraphs about the topic. There is not feedback on each individual question and why each incorrect answer is incorrect. If they just transferred the 73 questions to the main Uworld Qbank it'd be better. 2/5 stars.
That said, I don't know any better resources. My school just taught us sensitivity, specificity and thats about it. So I needed something to learn from. I don't necessarily regret buying it.
Also, the explanations in the UWorld biostats thing are so formal and textbook-like. Not my style. I fall asleep after reading 2 sentences.