Statistics: Effective Blocking

Objectives

• Students will be able to identify situations in which blocking will reduce variation.
• Students will recognize that some randomized block designs are useful in reducing variation while others are not.
• Students will recognize that random allocation of events occurs within each block.
• Students will recognize that the experimental units within each block are as similar as possible and different from the experimental units in the other blocks based on a variable that has the potential to affect the outcome of an experiment.

Vocabulary

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

About the Lesson

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

• Randomly allocate treatments and observe the mean number of mosquitoes in the lots after the sprays have been applied.
• Compare mean differences and variability for the three experimental designs to determine the most effective design for this context.