assign_treatment: Random treatment assignment with blocks

Description Usage Arguments Details Value Examples

Description

assign_treatment randomly assigns treatments to the units in the sample so to best maintain the equal proportions of conditions within each block. The function expects the user to provide a blocking object and treatment conditions.

Usage

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assign_treatment(blocking, treatments = c("Treated", "Control"))

Arguments

blocking

qb_blocking or scclust object with the blocked units.

treatments

character vector with treatment conditions.

Details

When the number of treatment conditions evenly divides the size of a block, the conditions will be repeated that many times within the block. For example, with three conditions, c("T1", "T2", "C"), and a block with six units, two units will be assigned to each condition.

When the number of treatment conditions does not evenly divide the block size, the conditions are repeated up to the closest multiple lower than the block size and the remaining conditions are chosen at random. For example, with the three conditions from above and a block with four units, each condition will be repeated once (since floor(4/3) == 1). One additional condition is needed to assign all units in the block, and that condition is selected at random from c("T1", "T2", "C") with equal probability. In a block with 8 units, each condition will be repeated twice (floor(8/3) == 2). Two additional conditions are now needed, and they are chosen from c("T1", "T2", "C") without replacement.

In all cases, the treatment conditions within a block are shuffled so that all units have the same probability of being assigned to each condition. Units not assigned to blocks will not be assigned treatments (indicated by NA).

Value

Returns a factor with the assigned treatments.

Examples

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# Example blocking
my_blocking <- qb_blocking(c("A", "A", "B", "C", "B",
                             "C", "C", "A", "B", "B"))

# Two treatment conditions
assign_treatment(my_blocking)

# Three treatment conditions
assign_treatment(my_blocking, c("T1", "T2", "C"))

# Four treatment conditions
# (This throws warning because some blocks contain less than four units)
## Not run: assign_treatment(my_blocking, c("T1", "T2", "T3", "C"))

fsavje/quickblock documentation built on May 8, 2019, 8:33 a.m.