Use the right unit
Enter unique visitors and the number of those visitors who converted in each independent randomized group. A person is either a converter or not; do not enter repeat transactions as converting visitors. The tool is for a binary outcome, not revenue per visitor.
Understand the result
The test compares two conversion proportions using a pooled standard error and a two-sided normal approximation. It reports the absolute percentage-point difference, relative lift, p-value and an approximate unpooled difference interval. A p-value is not the probability that a variant is the winner.
Respect the limits of the design
At least ten converters and ten non-converters in each group are required before this tool reports inference. Smaller samples need an exact method or more observations. Repeated peeking, multiple comparisons, overlapping users and non-random allocation can make the result misleading. Statistical significance does not establish commercial importance.