Framework library · Decision making and problem solving
Weighted decision matrix
A weighted decision matrix makes a choice between options explicit: list the criteria, agree how much each matters, score every option on every criterion and combine the weighted scores. Its value lies less in the final number than in the argument it forces. The weights show what the decision-makers think matters, and the scores show where the options differ.
Use it when
- You are choosing one option from three to six, such as a supplier, a site or a technology, and several factors matter.
- Different stakeholders weigh the factors differently and the disagreement needs to be visible.
- The choice must be explained afterwards to a board, an auditor or the suppliers who lost.
Avoid it when
- One factor dominates, such as price in a commodity purchase. Decide on that factor and skip the matrix.
- The outcomes of the options are uncertain and the uncertainty is the point. Use a decision tree or a Monte Carlo simulation.
- You are ranking a long product backlog. RICE scoring is built for that.
- The question is whether to build, buy or partner for a capability. Use build, buy or partner, which adds the questions specific to that choice.
How to run it
Agree the options and the criteria
Three to six options and five to eight criteria. Each criterion should be independent of the others: unit cost and total cost are one criterion, not two.
Set the minimums first
Anything an option must pass whatever else it offers, such as a quality floor, is a pass or fail test, not a weight. The workbench excludes any option that scores below 3 on quality.
Weight the criteria before scoring
Weights that add to 100 are easiest to read. Agree them before anyone scores the options, so they cannot be tuned to a favourite.
Score each option on each criterion
1 to 5, with a written definition of what a 1 and a 5 mean, and a note of the evidence behind each score.
Read the ranking and the margins
A lead of 0.1 on a five-point scale is a tie. Check which criterion decides it.
Test the weights
Change the weight you are least sure of by ten points. If the ranking flips, the decision rests on that weight and it needs a proper discussion.
Work through it
Answer the questions below, or load the worked example to see a finished one. The drawing updates as you type. Export the result as a PowerPoint deck, a Word document, an Excel workbook, a PDF or plain text.
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Mistakes to avoid
- Adding criteria until the favourite wins. Fix the list and the weights before scoring.
- Double counting. Unit cost and total cost of ownership, or lead time and responsiveness, measure much the same thing and inflate its weight.
- Treating scores of 1 to 5 as measurements. A 4 is not twice a 2, and small differences in the total are noise.
- Hiding a deal-breaker in a weight. If an option is unacceptable below a threshold, make the threshold a minimum.
Where it comes from
No single originator. Combining weighted scores across criteria is the linear additive model of multi-criteria analysis, set out for UK government use in Multi-criteria analysis: a manual (Dodgson, Spackman, Pearman and Phillips; commissioned by the Department for the Environment, Transport and the Regions in 2000 and reissued in 2009). A related engineering method, which scores concepts against a reference design, is Stuart Pugh's concept selection ("Concept selection: a method that works", International Conference on Engineering Design, Rome, 1981; Total Design, 1991). Source.
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Further reading
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