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Statistical concepts

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Last updated by Mark Maddren

Source: http://assessment.tki.org.nz/Using-evidence-for-learning/Concepts

Why do I need to know about statistical concepts?

The more you understand about statistical concepts, the greater is your ability to read and understand graphs and data sets, analyse results, and use your knowledge to further student progress.

This applies to educators at every level, whether teachers, school leaders, professional learning facilitators or education administrators.


Standards-based assessment

Standards-based assessment allows us to make judgments about the level of an individual's learning with respect to shared benchmarks of expected performance, supported by exemplars.

Reliability and validity

The reliability of an assessment tool is the extent to which it measures learning consistently. The validity of an assessment tool is the extent by which it measures what it was designed to measure.

Types of data

An important part of a well-designed analysis is to be aware of the types of data that are available, so that the appropriate analytic techniques are employed, and inappropriate ones avoided.

Mean, median, and standard deviation

Mean, median, and standard deviation

The mean and the median are both measures of central tendency. Standard deviation (SD) is a widely used measurement of variability used in statistics.

Percentages, percentiles and stanines

In order to understand and analyse data from an assessment tool, you need to know the differences between the ways that different tools measure student achievement, and what that might mean for your analysis.


Norms are statistical representations of a population, for example PAT maths scores for year 6 males, or e-asTTle reading scores for year 9 Māori females.

Effect size

A good way of presenting differences between groups or changes over time in test scores or other measures is by ‘effect sizes’, which allow us to compare things happening in different classes, schools or subjects regardless of how they are measured.