Informal inference occurs when, from the evidence collected (perhaps heights of year 8 students in our class), we make a generalised claim (perhaps about the heights of year 8 students across Australia). We cannot be absolutely certain about our claim.
From the early years when students start collecting their own data, they can ask about a wider context. For example, "Would the class next door or in the next school have the same data?"
Informal inference is about moving beyond the data collected (the sample) to a larger context (a population).
The three key elements of informal inference are evidence, generalisation and degree of certainty.
- Evidence is collected from distributions that display variation and expectation from the data.
- Generalisation is the claim made beyond the data collected to a wider population.
- Degree of certainty is related to the confidence in the process carried out. Random samples and larger samples engender more confidence in a generalisation.
Over the middle years, students learn about random samples from populations, about how to display the data appropriately to provide reliable evidence, and about building intuitions for how certain they can be with their informal inferences.
