In the Scenario Described Above, Instead of Using the Raw

In the scenario described above, instead of using the raw scores, the researcher used the percentile rank in the achievement test and grouped the students into three new groups: the top third, the middle third, and the bottom third. Then half of the students in each group were randomly assigned to use the new textbook. Which of the following methods of blocking is employed here?

A) Predefined value blocking
B) Predefined range blocking
C) Sampled value blocking
D) Sampled range blocking
E) Post hoc blocking method