**What is a 'Best/Worst Rank' question on OpinionX?**

Best/Worst Rank (also known as *MaxDiff Analysis*) ranks a list of options by asking participants to pick their most and least preferred option from a randomly selected shortlist of the options multiple times.

**When should I use a Best/Worst Rank question?**

Best/Worst Rank is ideally suited to ranking long lists of options because, instead of showing the entire list together (ie. Order Rank), it breaks it down into a series of quick and easy votes. It can generally be used in most of the same cases as Pair Rank, which uses the same underlying model to rank people's preferences (aka discrete-choice analysis). For example, Best/Worst Rank is often used by product teams trying to rank features by highest value or prioritize a list of feature ideas.

**MaxDiff Sample Size Calculator**

OpinionX has a free sample size calculator for our Best/Worst Ranking block type. Click the calculator icon on the Best/Worst Rank block during survey setup to make it appear.

The calculator uses the formula ** rx/np=s** to inform recommendations for your survey configuration:

= number of ranking options (eg. x = 11 in the screenshot above)`x`

= number of options per set (ie. options shown in each comparison vote)`n`

= number of participants that will complete your survey (minimum estimate)`p`

= robustness variable, ensures each option will appear in at least`r`

*r*comparisons total= number of sets per participant (ie. how many times they'll have to pick Best/Worst)`s`

We set ** r** to a default value of 200 across all surveys, which means that each option should appear in at least 200 best/worst comparison votes for your results to reach a robust sample size. You can use this formula to manually recalculate your own design configuration recommendations if you would like to use a different robustness variable.

# How are the Best/Worst Rank scores calculated?

The Best/Worst Rank block shows three key numbers on the Results Overview page: (1) Best, (2) Worst, and (3) Score. Best and Worst both calculate the percentage of appearances where an option received that choice, and "Score" is calculated using the formula* *. For example, if an option that appears in 20 voting sets is picked as "Best" 11 times and "Worst" 3 times, it's score would be (11-3)/20 = 40.

`best-worst/appearances`

Here's an example of a survey with some sample results data:

# What ways can I customize my Best/Worst Rank block?

Free Customization:

**• Question** → Set the context for how participants should interpret the options and vote.

**• Options **→ Add your ranking options manually or bulk copy/paste via the Import button.

**• Sets Per Participant** → Decide how many times each participant must pick the Best/Worst options (eg. "10" would mean they are shown 10 sets of options to vote on).

**• Show Description** → Add additional context below the question in an extra text field.

Premium Customization 💰 (Ask tier)

**• Custom Labels** → Replace "Best" and "Worst" with your own text.

**• Remove 'Skip'** → Hide the "Skip" button so that people are forced to vote every time.

**• Custom Set Size** → Change how many options are shown in each set (default: 4).

**• Survey Branching** → Send people to a specific block after they finish Best/Worst voting.