The decision tree: every question, every answer, every test
Questions run from left to right; the path lights up as you answer, and each leaf on the right is a test. On a phone, the tree scrolls sideways in its box.
The questions
What kind of outcome did you measure? Yes or no for each unit: converted, on time, correct
How many groups, and how were they scored? Two independent groups
The test
Two-proportion z test
Assumes
Independent units; at least 10 successes and 10 failures in each group.
Which test fits depends on what you measured, how many groups you compare, whether the groups are independent or paired, and whether σ is known. Answer one question at a time: the path lights up in the tree, and the leaf names the test with its assumptions, what to do if they fail, and the code. Or switch to the drill and name the test for a scenario yourself.