A worked distinction
A 2% observed basis over thirty days can be annualized arithmetically, but the annualized number does not establish that the trade can be repeated at the same price or financed at the same rate.
What to verify in your own analysis
Include entry and exit fees, collateral commitment, borrowing and settlement differences. A perpetual swap has no fixed expiry forcing its basis to converge at a chosen date.
Write down the market or protocol identifier, units, observation window and data source before comparing outputs. Keep unavailable values distinct from zero. Capture a baseline and change one assumption at a time so the resulting difference can be explained.
Use the linked working tools
Open the related tools below to inspect actual public observations or calculate a local scenario. The numerical example above is illustrative, not a current quote. Export the result together with its assumptions if you need a reproducible research record.
The review checklist records what you checked in this tab. Completion measures your own notes, not whether an investment is safe, suitable or profitable.