Course · 5. TURF (reach)
What TURF is
TURF stands for total unduplicated reach and frequency. It answers a line-up question: with room for k items, which k reach the most people? A person is reached when at least one item in the set is one they would buy.
The answer is rarely the k most popular items. Popular items often appeal to the same people, so the second favourite adds few new customers. An item that is only moderately popular, but with people the others miss, can add more. TURF scores whole sets, not items one by one.
Reach and frequency
- Reach: the share of people who would buy at least one item in the set. This is what TURF maximizes.
- Frequency: how many of the set's items a person would buy, on average. Two sets with the same reach can differ here: higher frequency means more of the set appeals to the same people.
Where the "would buy" comes from
Classic TURF starts from a yes / no per person and item: a purchase-intent rating above a cutoff, or items above a person's threshold in a MaxDiff study. In Chosŏn, TURF runs on a fitted menu model or a MaxDiff fit. On a menu fit: the menu simulator's 20,000 customers, each with their own lasting taste and a fresh occasion on every visit. That adds one thing a rating cannot: reach over several visits. How many customers buy from the set at least once in a month, not just on one visit.
On a MaxDiff fit, a person is reached when one of the set's items is among their top few (3 by default), since MaxDiff ranks the items without saying who wants them. TURF from ratings is not in Chosŏn yet.
Typical uses
- A range or line-up of a fixed size: flavors, a seasonal menu, a vending machine, a shelf.
- The audience of a promotion or loyalty offer built on a set of items.
- Checking whether a new item reaches new people or the same ones.
Next: Reach in Chosŏn