A two-stage, multilevel approach to random assignment is an intriguing way to test a complex set of interventions — such as interventions children experience in sequence as they move from preschool to kindergarten.
In the first stage of such a design, groups (schools or centers) of participants are randomly assigned to program and control groups.
But randomizing enough clusters (schools) to create three arms for testing the pre-K and kindergarten programs would have been challenging in its operational demands and use of resources.
Randomly assigning children to kindergarten math clubs within the program arm allowed for reasonable statistical power while balancing the reality of implementing the clubs in so many schools.
Interesting alcohol related fact: A brewery tank ruptured in a London Parish in 1814, releasing 3,500 barrels worth of beer, destroying two houses and killing nine people.
In this section, we look at some different ways to design an experiment.In the second stage, individuals within those groups (students or children) are randomized to two different conditions.This design creates up to four groups — a group that receives both interventions, a group that receives the first intervention but not the second, a group that receives the second intervention but not the first, and a control group.Many of the teetotallers had their own reasons for not drinking alcohol, meaning that the scientists would have had to either force them to drink (highly unethical) or drop them from the study, leaving them with just drinkers who they would have had to convince not to drink, this dictation of a way of life could again be highly unethical.So we can see just how difficult it is to use random assignment in some cases, yet in others experiments wherein the participants past cannot make a large impact, I consider it to be the best assignment type available.So by not using the correct method, the studies found a connection that was in fact not there.Random assignment would have shown that this connection did not exist, any other assignment could have left the bias intact.Moreover, the design minimized the loss of power from attrition of children across years.As children moved from pre-K to kindergarten, randomizing again in the kindergarten year meant that only children who stayed in the sample for kindergarten were randomly assigned, minimizing attrition and maximizing power.This design created three research groups at the end of kindergarten: (1) children with two years of math enrichment (Making Pre-K Count in pre-K and High 5s in kindergarten), (2) children with one year of math enrichment (Making Pre-K Count in pre-K only), and (3) children with no math enrichment (a control group with pre-K and kindergarten as usual).The benefits of a two-stage multi-arm design The two-stage, multi-arm random assignment research design made it possible not only to learn whether the specific interventions worked, but also to build evidence about the combined effect of two well-aligned educational programs over time. We used the cluster-level design in testing the pre-K curriculum to minimize program spillover from one classroom to another.