What We Know

This summary focuses on computational estimation, which involves finding an approximate value for the result of a computation and may involve addition, subtraction, multiplication or division of whole or rational numbers. Estimates are useful when exact answers are impossible, unrealistic or unnecessary. Estimates are also useful to check an answer' reasonableness.

Traditionally, mathematics instruction has focused on obtaining correct answers. However, an emphasis on computational estimation would benefit students and is a skill students lack. On one administration of the National Assessment for Educational Progress (NAEP), only 24% of 13 year olds identified that would be close to 2. The majority of students estimated the answer as 1, 19 or 21. (Carpenter et. al, 1981).

Research also shows that students who are good at computing exact answers are not necessarily good at estimating or judging answers' reasonableness (Reys & Yang, 1998).

Furthermore, in addition to the uses of estimation included in the first paragraph, the development of estimation skills appears to correlate with the development of other mathematical skills and concepts. Studies indicate that computational estimation and mental computation promote students' number sense (Reys & Reys, 1986; Sowder & Wheeler, 1987). Instruction that integrates mental computation, computational estimation and emphasizes the relative magnitude of numbers has been shown to lead to an increase in student performance in numeric situations (Markovits & Sowder, 1994). Seventh-grade students provided instruction on computational estimation were more likely to use and continue to use strategies demonstrating sound number sense (Markovits & Sowder, 1994). Research also shows a correlation between students' estimation skills, their computational skills and mathematics SAT scores (Hanson & Hogan, 2000).