Advanced Research

Interpreting Part-Worth Utilities from MNL Output

Updated

Read the part-worth utility for each level — what the numbers mean, why they're centered on zero, and how to use the standard errors.

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Overview

Read the part-worth utility for each level — what the numbers mean, why they're centered on zero, and how to use the standard errors beside them.

Step-by-step

  1. Open the conjoint card in Results and find AGGREGATE LOGIT UTILITIES. Part-worth utilities with standard errors

  2. Read each level's utility — e.g. Storage: 128GB −0.12 ±0.07, 256GB +0.03 ±0.07, 512GB +0.09 ±0.07.

  3. Read the sign against zero — utilities are zero-centered within each attribute, so positive means "preferred relative to that attribute's average", negative means the opposite.

  4. Compare within an attribute, never across — the gap between 128GB and 512GB is meaningful. "Storage 512GB (+0.09) vs Price $699 (+0.04)" is not a valid comparison; that's what importance scores are for.

  5. Use the ± standard error — if two levels' utilities are within about one SE of each other, treat them as effectively tied.

Tips

Tip: Look at the ordering first. Utilities that don't follow a sensible monotonic order where they should — e.g. a higher price scoring better than a lower one — usually signal a design or sample problem, not a genuine insight.

Note: Utilities live on the logit scale. They're not dollars, not percentages, and not ratios — a +0.09 isn't "9% better". They only mean something relative to other levels in the same attribute, or run through the simulator.

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