RANGE MODEL / SCENARIOS
Which Input Changes the Decision?
Choose a plausible change to one assumption. Hold the others still. See how far the result moves — and whether the decision moves too. The size of the change you choose affects the comparison.
ONE DIAL MOVES. EVERYTHING ELSE STAYS STILL.A number built from assumptions.
Fictional 12-month example from the talk. The best-supported case starts at 140 additional sales.
At £60 contribution per sale and £8,000 cost, practical break-even is 134 sales.
Cost, contribution and decision threshold
Contribution = sales × value per sale. Net contribution = contribution − project cost. Practical break-even rounds cost ÷ value per sale up to a whole sale.
Pick one assumption.
Other inputs are held at their base values. This isolates impact; it does not tell you which assumption is most likely to be wrong.
Click rate (CTR)
Base value: 5%. Change this alone.
STILL FIXED Additional impressions · Conversion rate · Contribution per sale · Project cost
Did the decision move?
£400 net contribution
£400 net contribution
Click rate (CTR): 5 → 5 %. All other assumptions stay at their base values.
Sales movement: +0 (0%). Net contribution movement: +£0.
Break-even: 134 salesBase: meets threshold · Revised: meets threshold
Which tested change mattered most?
Ranked by the changes you tried, using absolute movement in net contribution. Different change sizes can change the ranking. This is not a universal ranking of SEO inputs.
Move a dial and answer the short question to record a test. Then try a second assumption.