Course · 3. Menu-based choice (MBC)
Your menu data
Chosŏn reads one row per item on each menu a respondent saw:
| resp | menu | item | price | bought |
|---|---|---|---|---|
| 1 | 1 | Sandwich | 4.50 | 1 |
| 1 | 1 | Salad | 6.25 | 0 |
| 1 | 1 | Crisps | 0.96 | 1 |
| 1 | 2 | Sandwich | 3.60 | 0 |
| 1 | 2 | Salad | 5.00 | 1 |
| 1 | 2 | Crisps | 1.20 | 0 |
menunumbers the menus in the order the respondent saw them. The model uses that order.boughtis 1 for every item ticked, 0 otherwise. Ticking nothing is a valid answer.- Bundles (a meal deal, a package) are items with their own price, varied like any other. An optional
containscolumn on their rows names their items, joined by+, e.g.Sandwich+Crisps+Juice; leave it blank for other items. Chosŏn then counts units of each item (bought separately plus inside bundles). - For now every menu must list every item, and every respondent must see the same number of menus (at least 4, or 5 to keep one back for the holdout check). Menus that hide some items are on the list for later.
Designing the survey
- Vary each item's price on its own, across a few levels around the usual price (the tutorial uses 80%, 100% and 125%). An item whose price never moves gets no price effect.
- Show each respondent several menus (the tutorial uses 10). More menus per person sharpen what carries over from visit to visit.
- Aim for 200 respondents or more. Links between items need more data than buy rates do.
The data check
Before fitting, Chosŏn checks the format and warns about weak spots: items almost never or almost always bought (their links are hard to estimate), prices that never vary, a bundle that is never cheaper than its items, too few menus for a holdout, too few respondents.
The base price of each item is the median price shown. Results such as buy rates are reported at base prices, and the simulator compares every scenario with the base menu.
Size limits
Free plan: up to 300 respondents, 12 menus and 12 items. Premium: up to 5,000 respondents, 20 menus and 40 items. Menu fits run on our servers' CPUs on every plan; the tutorial (300 respondents, 10 menus, 9 items) takes a few seconds.
Try it in the tutorial: the data
Next: The menu model
Tutorial links open the example project in the app; it is free and needs a free account.