Course · 5. TURF (reach)

Reach in Chosŏn

TURF is the Reach (TURF) tab of a menu study's results.

Settings

  • Visits per customer (1 to 8). With 1, reached means buying from the set on a visit. With more, buying from it at least once over that many visits.
  • Largest set: the search finds the best set at every size up to this one.
  • In the search, per item: a candidate, always in (an item you will keep anyway, so the search builds around it), or left out. A bundle in a set brings its items with it.
  • Model: ours, or the standard model that treats every visit as a new customer.

Prices are the base prices.

Results

  • Best set at each size, with its reach, the reach added by the last item, and frequency (items bought per customer). The added reach usually shrinks with each item. The size where it gets small is a natural place to stop.
  • Close alternatives at one size: the next best sets, each with how far it is behind the best. The search tries every set when there are few, and otherwise uses an exact solver with a time limit. Sets it could not prove best are marked "best found".

Example: the café

With 1 visit, the best single item is Coffee (41% of visits), then Sandwich and Coffee (61%), then adding Salad (73%) and Soup (80%). All nine items together reach 94%. Over 4 visits, Sandwich and Coffee already reach about 95% of customers.

The data was simulated, so the truth is known. The per-visit sets are the same in the truth, with reach within a point. Over 4 visits, the best single item reaches 78% in our model and 78% in the truth. The standard model says 88%, because it counts a regular coming back as a new customer each time.

Reading it

  • Ties are common. Each reach has a 95% range, and each close alternative shows how far it is behind the best with a range of its own. At 3 items over 4 visits, Sandwich, Salad and Coffee is 0.02 points behind Sandwich, Soup and Coffee, with a range of -0.6 to +0.6: a tie (and the truth's best set). Choose between tied sets on cost, margin or operations.
  • Reach is not revenue. A set can reach many people who each buy little. Check the set in the simulator.
  • The rest of the menu does not change a set's reach. Taking an item off the menu moves no one to other items here (the survey measures switching through prices only). That is also the standard TURF assumption.

Next: When it helps

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