Write a reproducible note
A useful chart note lets someone else follow your steps. It distinguishes what you can measure from what you suspect and what you still do not know.
Leave a clear trail from observation to calculation.
Start with the idea
Start with the source, series, period and unit. Record the exact observations used in the calculation. “The line rose a lot” cannot be reproduced. “A rose from 100 at observation 1 to 120 at observation 4, a 20% increase” can be checked directly.
Next separate observations from explanations. An observation is that the recorded value changed. An explanation is a proposed reason. A chart alone rarely establishes why the change happened. Label possible causes as hypotheses and name the evidence that would help test them.
Include unknowns that could change the interpretation. These might be missing observations, a revised data definition, unrecorded costs or an unmatched time period. An unknown is not a reason to abandon the note; it is part of a careful account of its limits.
Keep the wording proportionate. An educational calculation describes its inputs. It does not establish what an asset will do next or whether someone should buy it. Finish with the next check you would make rather than a prediction that the evidence cannot support.
A worked example
“Illustrative series A, observations 1–4, GBP. The value rises from £100 to £120: (£120 − £100) ÷ £100 × 100 = 20%. It falls from £110 to £105 between observations 2 and 3. The reasons for the movements and values between observations are unknown.”
Your turn
Use the Observation Card to record a period, unit, two measurable facts, one hypothesis and the information you would need next.
Open the exercise tool →Show the answer and reasoning+
A reproducible answer names the selected chart and its period, gives two values or calculations that match the table, and labels the hypothesis as unverified. There is no single correct hypothesis. The important distinction is between a measured fact and a possible explanation.
Make your reasoning easy for another reader to check.
Related term
ReproducibilitySources & review
Original Charts Haven example. All stated numbers are illustrative and allow you to repeat the calculation.