Developing an understanding in number

2. Estimation and the development of a sense of number

Estimation is an important skill to develop throughout all year levels. In order for your child to improve his/her estimating skills, it is important that he/she estimates likely answers before doing the calculations.

For example:

• Your child should estimate, calculate, then compare the estimate and the calculation.
  
  
• This provides information on which to base the next estimate and so possibly improve the accuracy of the estimating skill.
  
  
• Supervise your child, checking to see that he/she follows the above procedure.
  
  
• Comparison of estimates and actual calculation will develop and over time, a high level of estimation skill.
  
  
• Encourage your child to use the calculator to quickly check a result after an initial estimation has been made. This estimate, calculate and compare cycle will improve your child’s skills and confidence with estimating mentally.

Estimation in measurement

Children should learn that estimation involves informed judgment rather than guessing and that we make an estimate so that we will not have to go to the effort of making a measurement. If we are confi dent that our estimate is sufficiently close to serve the purpose, more precise measuring is a waste of time.

The way we become confident of our estimates is to practise making them. This involves making estimates, measuring in order to gain feedback on how close we are, and incorporating the information into the next estimate so that we improve. Efforts to improve estimation skills by measuring after estimating should be made explicit so that children do not develop the mistaken views that we would normally do both, that measuring is somehow better than estimating, or that an estimate is ‘wrong’ if it is not the same as the measurement. It is important that children realize that the suitability of an estimate depends upon whether it is sensible for the use to which it will be put and how close it is to the ‘real’ measurement.

You can assist your child to develop and improve his/her estimating skills by:

• giving an emphasis to estimating
  
  
• establishing a sense that estimating skills can be improved by comparing the estimate with the actual measure so that estimates become increasingly reliable
  
  
• encouraging a sense of the measuring unit through regular experiences with commonly used measuring units.