EXAMPLE 3.20

Blocking in an education experiment. The Tennessee STAR class size experiment (Example 3.8, page 172) used a block design. It was important to compare different class types in the same school because the children in a school come from the same neighborhood, follow the same curriculum, and have the same school environment outside class. In all, 79 schools across Tennessee participated in the program. That is, there were 79 blocks. New kindergarten students were randomly placed in the three types of class separately within each school.