Almost 60 years ago, Danish mathematician Georg Rasch had an idea that he believed would revolutionise educational and psychological measurement.
Today, Rasch Measurement provides the foundation for many large-scale international and national student assessment programs and commercial tests, and is used in a wide range of research studies in education, psychology, medicine and social science.
Before we explain why you should delve deeper into Rasch Measurement Theory, let’s look at a definition.
What is Rasch Measurement?
In 1960, Rasch proposed a measurement model in which the probability of a person succeeding on a task is a function (f) of the difference between that person’s ability and the task’s difficulty:
probability of success = f(person’s ability – task’s difficulty)
For people with abilities much greater than a task’s difficulty, the modelled probability of success is high. For people with abilities well below a task’s difficulty, the probability of success is low. When Rasch’s model is applied to a set of test data, an estimate of each person’s ability and each task’s difficulty is obtained.
It turns out that the function (f) in Rasch’s model gives it unique and remarkable properties. Rasch himself observed that, when the model is applied to a reading comprehension test, it introduces the possibility of ‘the reading accuracy of a child [being] measured with the same kind of objectivity as we can tell his weight’.
The ‘objectivity’ to which Rasch refers is the possibility of measuring and comparing the abilities of test takers even if they haven’t completed the same set of test questions.
This simple description of the Rasch model is only the tip of the iceberg. New applications are being made continually across disciplines in a bid to better understand data and make that data more meaningful.
You don’t need to be a mathematician or statistician to recognise Rasch Measurement as a valuable tool. It can be a game changer for researchers, teachers, curriculum leaders, principals and social scientists, to name but a few. It’s been used to measure personality disorders, student learning and even the romance on the Bachelorette Australia.
In other words, if you have something to measure, you need to understand Rasch Measurement.
Reasons you should learn about Rasch Measurement
It underpins student testing globally.
‘With increasing use in schools and education systems of student progress and achievement data, it is vitally important that more people have an understanding of the theories and techniques that are used in assessment programs such as NAPLAN and NAP Sample assessments.’
Robert Randall, CEO, Australian Curriculum, Assessment and Reporting Authority (ACARA)
Rasch Measurement has been used in a wide range of testing and assessment programs, including the Progressive Achievement Tests (PAT), NAPLAN, PISA and TIMSS. It is used in the design and administration of test items, as well as to analyse test data once collected. For education professionals seeking a practical understanding of how widely-used assessments are analysed, learning about Rasch Measurement is a great move.
You can create more robust assessments.
Is a test or other measuring instrument measuring what it is meant to measure? Is it free from bias? Rasch Measurement provides an excellent tool for investigating the robustness of assessment instruments and for constructing more effective tests. For educators, this means you can construct better measures of student learning.
You can use data to improve teaching and learning.
Rasch Measurement not only enables you to create more effective tests; it also can provide a better understanding of test results. It empowers you to turn data into actionable information to help teachers (you or your staff) modify their practices and improve student learning.
You can develop your statistical analysis skills.
If you want to succeed in your career, whatever your field, you are likely to benefit from better measures of the variables that matter to you. When you learn about Rasch Measurement, you are learning about objectivity in measurement and how to evaluate the consistency of data. This is important for measuring group trends and individual growth over time, and for item evaluation, construct validation, item banking and test equating.
“The family of Rasch measurement models is a way to make sense of the world.”
Wright and Mok (2004)
What more reason do you need?
Delve deeper into Rasch Measurement with ACER’s new masters level course Understanding Rasch Measurement Theory. With 100% online part-time study, you can complete the course in just 10 weeks while you advance your career.