MEASUREMENT: INTRODUCTION

The activities in this section are concerned with the measurement of length and angle.

Practical measuring activities relating to length, weight, capacity etc. have long been a common feature of the mathematics work in Infant classrooms and are usually well represented in the published materials available to schools. Unfortunately, soon after this, in the Junior years, it is all too often assumed that most children know what measurement is and have clearly grasped the need for standard units of measure. As a result, much of the work presented to children in this age group tends to consist of manipulation of standard units (more 'sums' in disguise) and practice in the use of ready-made measuring instruments. Experience indicates that, in many cases, such assumptions are unfounded. The essential ideas involved in measurement (the comparison and quantification of continuous quantities) are subtle and will be learned by children not from teacher explanation; but by experiencing them over a protracted period of time in many different contexts.

The ideas in measurement are:

1. Measurement is essentially an approximate affair. All measurements are inherently inexact. 'Progress' in coming to terms with measurement therefore typically takes the form of a sequence of activities beginning with crude global comparisons ('bigger than', 'lighter than' etc.), leading to the use of arbitrary units.
2. No particular magic resides in the use of standard units such as the centimetre, kilogram or litre. These are adult conventions and all the basic work on measurement done with young children could readily be done with informal units that are meaningful to them - the ideas involved are exactly the same. Indeed, the continued use of informal units beyond the Infant years may help many children to eventually realise this. (At some stage the 'turtle unit' could be redefined to emphasise the arbitrary nature of such units).
3. The approximate nature of such measurement implies that any measurement involves an 'error' - not a mistake but simply a discrepancy between what was expected and what was obtained, or between an estimate and an actual measurement. Such 'errors', or deviations, will normally become smaller and smaller, the degree of accuracy obtained being eventually expressed using decimal numbers.
4. Throughout all measuring activities, estimation of quantities before measurement is of vital importance. Estimation is an essential component of every activity and the natural unit of length in this context is the 'turtle unit'. In the case of the Valiant Turtle this is very close to a centimetre so that the link with standard units can be readily made when needed.