Crossover randomized design
Randomly assigned participants switch treatment regimens after wash-out periods
Crossover randomized designs are more complex and rigorous to conduct that traditional experimental research designs. At the beginning of the trial, study participants are randomly assigned to treatment groups. The respective interventions (or lack thereof) are given to the participants and after a pre-specified period of time, the intervention is stopped.
In crossover randomized designs, this stop in the intervention is known as the "washout" period. Washout periods allow for the initial treatment effects to be "washed out" or dissipate. The length of time for the "washout" period will vary from study to study. Researchers are cautioned from having too short and too long of a "washout" period. Use sound empirical reasoning to decide how long the "washout" period should be or seek out crossover trials in the empirical literature to find a valid period of time.
Then, the treatment groups switch. Those treatment groups that were first receiving the respective intervention (or lack thereof) before the "washout" period are given the other intervention or control treatment. This "crossover" from treatment to control or control to treatment is where the name "crossover randomized design" comes from.
Crossover randomized designs can suffer from carryover effects from the first intervention to the second intervention. However, crossover randomized designs are extremely powerful experimental research designs. Statistical power is increased in this experimental research design because each participant serves as their own control.
In crossover randomized designs, this stop in the intervention is known as the "washout" period. Washout periods allow for the initial treatment effects to be "washed out" or dissipate. The length of time for the "washout" period will vary from study to study. Researchers are cautioned from having too short and too long of a "washout" period. Use sound empirical reasoning to decide how long the "washout" period should be or seek out crossover trials in the empirical literature to find a valid period of time.
Then, the treatment groups switch. Those treatment groups that were first receiving the respective intervention (or lack thereof) before the "washout" period are given the other intervention or control treatment. This "crossover" from treatment to control or control to treatment is where the name "crossover randomized design" comes from.
Crossover randomized designs can suffer from carryover effects from the first intervention to the second intervention. However, crossover randomized designs are extremely powerful experimental research designs. Statistical power is increased in this experimental research design because each participant serves as their own control.
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