Estimating

Estimation skills correlate with numerical understanding and overall math achievement skills. Estimation is a problem solving skill. It involves observation, the ability to gather and assess data, and the opportunity to use that data to arrive at a conclusion, which can be explained to others.

There are actually three estimation skills: numerosity, meaurement, and computational estimation. Numerosity and meaurement estimation are related to spatial abilities, and are the types of measurement more relevant to grade 1.

Estimating on a number line is included in the number line section, although it has some similarity to these other concepts. To develop good estimating skills, children need a flexible referent they can compare with. A referent is a personal item that is used to estimate, whether a physical entity or mental construct.

Some students naturally make referents, but others are slower to to pick up on this construction. For this reason, estimating activities benefit from more discussion than some teachers normally provide. After making an estimate, they need to share their strategies and hear other viewpoints.

‘I thought 4 should cover the bottom, and maybe there are 5 deep so 20’

‘My handful might be 10, and I thought there would be 5 handfuls in the jar’

For younger students, we can provide a referent for them by showing them 5 marbles, or first letting them see how many fit in their hand. The numbers students are working with should be very familiar to them.

Some research suggests that students should start off choosing a range for their estimate, not an exact number. The range can be narrowed as students gain experience. A concrete number line or hundred board can be great tools for choosing a range.

Purpose / referent / chunking / diverse experiences / accept a range / discussion
estimation should not be standalone but connected to numbers they are working with
repetition – of same activity, of same with different object
part whole estimation

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