Assignment to treatment and control is conditionally random. Conditions to be satisfied are:
(1) Each site has two treatment modules and two control modules
(2) All sections at a site have the same assignment (either treatment or control) for a given module
Given these constraints and the fact that there are four modules, there are six possible patterns to use to randomly assign sites to a set of treatment and control modules: TTCC, CCTT, TCTC, CTCT, TCCT, CTTC. The randomization procedures was as follows:
(1) Sites are matched together so that the number of students enrolled at one site is roughly equal to the number of students enrolled at another site. For example, if one site has a projected enrollment of 35 students, a second site has a projected enrollment of 37 students, and a third site has a project enrollment of 70 students, then the matching algorithm would place sites 1 and 2 into the opposite randomization pattern as site 3.
(2) One half of each site match is randomly assigned a pattern via a computerized random number draw that simulates the roll of a 6-sided die. Once one half of the match is assigned a pattern, the other half's randomization pattern is set.