Empirical Analysis of Drill Ratio Research: Refining the Instructional Level for Drill Tasks

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NICHCY’s Structured Abstract 28 describes the following:

Title | Empirical Analysis of Drill Ratio Research: Refining the Instructional Level for Drill Tasks

Author | Burns, M.A.

SourceRemedial & Special Education, 25(3), 167-173.

Year Published | 2004

Providing students an appropriate level of challenge, called the instructional level, is an important component of effective instruction. Research regarding the optimal ratio of known to unknown items for drill tasks has been inconsistent. The author of the current article conducted an empirical meta-analysis of research on drill ratios by using the following groupings: < 50% known, 50% to 69% known, 70% to 85% known, and 90% known. Fifty-five effect size coefficients were computed, after eliminating outlying data, from 13 articles, with the 3 least challenging ratios resulting in strong mean effects. The most challenging (< 50% known) ratio resulted in a small to moderate effect. A mean effect size of .82 computed for various student outcomes compared to .43 for student preferences. Much stronger effects were also noted for tasks involving acquisition of new skills compared to proficiency tasks. Implications for research and practice are discussed.

The concept “instructional level” or “appropriate level of challenge” was first discussed in educational literature in the 1940’s and its definition has been refined many times since then. In this meta-analysis, instructional level is explained as the comfort zone in which a student has sufficient background knowledge and skills to be successful at a task while still learning new material. Researchers have theorized that students’ instructional level for particular tasks can be explained as a ratio between known and unknown material. For example, one theory holds that the instructional level for reading is between 93 and 97% known words and 3 to 7% unknown words. Many different ratios have been suggested to be optimal for drill tasks, ranging from 90% known material and 10% unknown material to 50% known and 50% unknown material. Establishing an instructional level for drill tasks could increase their efficiency and that is what this meta-analysis sets out to do.

Research Questions
The purpose of this study is to determine the appropriate instructional level to implement drill tasks. The research questions were:

  1. Of the drill ratios found, which led to the largest effect? (Drill ratio refers to the ratio of known and unknown information in a drill task)
  2. Which type of dependent variable studied, academic outcomes or student preferences, led to the strongest effect?
  3. In which stage of learning were the effects of using drill tasks strongest?

Research Design

  • Number of Studies Included | 13
  • Number of Subjects | N/A
  • Years Spanned | 1978-2003

Research Subjects
Students participating in drill tasks.

Age/Grade of Subjects

Specified Disability
This study did not focus on children with disabilities.

Participants were drilled on information that they learned. Participants knew less than 50% to 90% of the information they were drilled on. Drills also occurred during the acquisition (learning new target behaviors to a high level of accuracy through shaping and consistent use of cues) and proficiency (increasing accuracy and fluency) stages of learning. The effect of dependent variables (academic outcomes and student preferences) was also researched.

Duration of Intervention

The current data suggest that drill tasks are more effective in the acquisition stage of learning than in the proficiency stage. It was also found that drills had a stronger effect for academic outcomes over student preferences.

Combined Effects Size

  1. Drill ratio:
  2. Stage of Learning: Acquisition = 1.09; Proficiency = 0.39;
  3. Dependent Variables: Academic outcomes = 0.82, Student preferences = 0.44.
  4. The overall effect size of drill tasks = 0.75.


  1. Drill tasks in which 50-90% of the material was known by the student were highly effective. Drill tasks when less than 50% of the material was known were significantly less effective.
  2. Drill tasks were more effective at the initial learning/acquisition stage than at the rehearsal/proficiency stage of learning.
  3. Burns suggests more research should be done to investigate the effects of various drill ratios in proficiency tasks, maintenance tasks and generalization tasks. Proficiency tasks need to be researched further because the least effective drill ratios were often used in proficiency tasks in these studies, which may explain why drill tasks appeared ineffective at the proficiency stage in this meta-analysis. No studies examining drill tasks used for maintenance and generalization were found for this meta-analysis.


* Meta-Analysis | A widely-used research method in which (1) a systematic and reproducible search strategy is used to find as many studies as possible that address a given topic; (2) clear criterion are presented for inclusion/exclusion of individual studies into a larger analysis; and (3) results of included studies are statistically combined to determine an overall effect (effect size) of one variable on another.

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