Conjoint tasks

Random profile pairs (or k-tuples) over the supplied attributes, the design for a forced-choice conjoint. Profiles are sampled uniformly and independently per attribute; set a seed beforehand for a reproducible design (the function never sets one). At administration, fresh profiles are drawn independently for every respondent from the same attribute levels.

Usage

conjoint_design(attributes, n_tasks = 5L, profiles_per_task = 2L)

Arguments

attributes

Named list of level vectors, with at least two attributes. Attribute names must be unique and nonempty and must not be task, profile, persona_id, or chosen, which name the design's own columns. Each attribute needs at least one level, and its levels must be unique, nonempty, and not missing.

n_tasks

Tasks per respondent: one whole number of at least 1.

profiles_per_task

Profiles shown per task (default 2): one whole number of at least 1. conjoint_instrument() needs at least two.

Value

A conjoint_design list with fields profiles, a tibble containing task, profile, and one column per attribute, and attributes, the named list of attribute levels. Render it into forced-choice items with conjoint_instrument() and estimate with conjoint_amce() after administration.

Details

Within a task, a profile that repeats one already drawn is redrawn, up to 25 times. When the attribute space holds fewer distinct profiles than profiles_per_task, every task repeats a profile. Otherwise a repeat remains only when all 25 redraws repeat a profile, which can happen when the space is barely larger than the task. Either case draws a warning that says which occurred. The profiles drawn for each respondent at administration follow the same rule without a warning.

Examples

set.seed(110)
conjoint_design(
  list(price = c("$10", "$20"), speed = c("slow", "fast")),
  n_tasks = 4)