Lesson 3.7 – How to Experiment Well

  • Describe how to randomly assign treatments using slips of paper or technology.
  • Explain the purpose of random assignment in an experiment.
  • Identify other sources of variability in an experiment and explain the benefits of keeping these variables the same for all experimental units.


Activity: Is anchored putting better? Part 2 

Today’s lesson is pretty straight forward.  Since students have already learned about how to conduct a simple random sample using a random number generator or slips of paper, it was easy to extend that knowledge into how to conduct random assignment.  Key things to keep in mind when describing random assignment:

  • Slips of paper should be the same size.
  • Slips should be mixed well.
  • Groups must be equal size.
  • Ignore repeats when using a random number generator.

Using random assignment helps to reduce confounding by creating roughly equivalent groups but it is also important to keep as many other variables the same in order to 1.) prevent confounding and 2.) reduce variability.


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