A conversion comparison is only as honest as the dates you feed it. We ask every client to lock three things before exports leave their system: the start and end dates, which payment methods were actually offered on each day, and any known outages.
Promotions skew more than people admit
A free-delivery weekend can lift wallet completion simply because returning customers already stored a wallet credential. That is useful context, not a reason to discard the week — but it must appear as a caption on the chart, not a buried footnote.
Outages need a red line
If a wallet provider failed for nine hours on a Friday, we either exclude the day or annotate it. Silent inclusion is how board packs accidentally “prove” that cards outperform wallets.
Minimum volume before we cut further
We rarely recommend device or region cuts until each method clears a volume threshold agreed in the engagement letter. Thin bars look dramatic in pop-art colours and still mislead.
When you request a study, bring a draft window and a list of known incidents. We will push back if the window is too short to support the decision you want to make.