MaxDiff vs. Conjoint vs. NPS: Which Instrument Matches the Decision
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An insights lead scoping a study has three common instruments to choose from, each answering a different question. Picking the wrong one does not just weaken the results: it fields a study that cannot answer the business question, after the programming and recruiting budget is already spent.
What each instrument actually measures
- MaxDiff (best-worst scaling) asks for best and worst items from rotating subsets and estimates relative item preferences. Forced choices can reduce rating-scale response habits; stimulus wording, presentation order, and brand context can still create halo effects.
- Conjoint analysis (including discrete choice) shows respondents full product or offer profiles built from varying attributes and prices, then asks them to choose between profiles. It estimates each attribute level's utility, letting a team simulate trade-offs such as how much a price increase needs to be offset by an added feature.
- Net Promoter Score (NPS) summarizes stated recommendation propensity. It is a proxy for loyalty or satisfaction, so track sample composition and uncertainty and pair it with actual retention or repeat purchase when those behaviors matter.
quantilope's comparison frames the MaxDiff-versus-conjoint choice around whether the goal is prioritizing items or estimating trade-offs among interacting attributes; aytm's guide makes the same distinction from a survey-design angle. Neither method substitutes for NPS.
A decision table, not a preference
| Question you're actually asking | Instrument | What it will not tell you |
|---|---|---|
| "Which of these features matters most?" | MaxDiff | Price sensitivity or combined attribute trade-offs |
| "How much would customers pay for feature X, and does it beat a price cut?" | Conjoint / discrete choice | A stable ranking of unrelated items outside the tested attribute set |
| "Is stated recommendation propensity changing?" | NPS | Actual retention or which intervention caused a change |
Treat this table as a first filter, not a substitute for the two guides above, which go deeper into sample-size and attribute-count tradeoffs than a summary table can.
Where Does the Cost of Choosing the Wrong Instrument Show Up?
The failure mode is rarely a survey bug. It's fielding the wrong instrument: a full discrete-choice conjoint when a simple MaxDiff ranking would answer the question, or an NPS trend stretched to justify a feature trade-off it was never designed to measure. Both mistakes surface only after the study is in field, when there's no cheap way back.
Where Does a Pre-Fieldwork Check Fit In?
A simulated comparison can inform candidate hypotheses when the outcome matches the intended task. A human comparison should test agreement and possible failure. A MaxDiff ranking, conjoint trade-off, and NPS score remain different estimands; converting one into another changes the question.
For Subconscious or another vendor, confirm the current deliverable in the study brief: respondent population, design, estimator, uncertainty, and whether item scores, part-worths, or longitudinal tracking are included. A general platform description does not establish availability or absence of each packaged output.
Choosing between the three, in practice
- Write down the decision in one sentence: ranking, trade-off, or relationship tracking.
- Match the sentence to the instrument above. Resist the urge to pick the method the team already has a template for.
- If the decision and stimulus are still fuzzy, sharpen the target group and stimulus definition before writing a single survey question, not add a fourth method to the study.
- If using simulation to shortlist options, predeclare the rule, retain a protected baseline, and carry forward options with uncertain estimates or important business constraints. Record exclusions. A noisy low score can discard a useful candidate and bias the later comparison.
Next step
See how a causal experiment frames a trade-off question before fieldwork, or how prior studies used real-human validation to confirm a simulated result. For hands-on scoping, book time to walk through a specific instrument decision, or read how the method works.