Education Technology

Statistics: Blocking Introduction
by Texas Instruments


  • Students will recognize that blocking can reduce variation.
  • Students will describe random allocation of treatments as occurring within each block.
  • Students will recognize that the experimental units within each block are as similar as possible and as different as possible from the experimental units in the other blocks based on a variable that has the potential to affect the outcome of an experiment.


  • experiment
  • experimental units
  • random allocation
  • randomized block design
  • simple random sample
  • treatments

About the Lesson

This lesson involves investigating the effectiveness of two mosquito sprays in a large tract of land by using two different experimental designs - one randomized design and one randomized block designs.
As a result, students will:

  • Select a random sample to be used in an experiment.
  • Randomly allocate treatments and observe the mean number of mosquitoes in the plots after the sprays have been applied.
  • Examine a sampling from a population and observe a pattern in a measured variable regardless of assigned treatments (i.e., more mosquitoes closer to the swamp).
  • Compare the variability in a completely randomized design with a randomized block design.