Diagnostic Assessment

How do you know what your students already know before your course begins?

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Prior knowledge and misconceptions

There are several important reasons you might want to use diagnostic assessments to find out what your students already know.

Prior knowledge

The simplest reason is to determine what content you may need to include or can leave out if students already know it.


Students are not empty vessels that you pour information into but actively make meaning of the world around them (see Constructivism). If their prior knowledge about the topic is correct, then it’s a benefit to the limited teaching time you have since you can move on to subsequent topics. If, however, students have misconceptions about the topic, these will prevent students from building correct understandings on top of these foundational but incorrect ideas. Therefore, it’s best to determine before the course begins what misconceptions students hold and how prevalent these are.

There are several methods to effectively help students change their misconceptions. While you can read more here, most methods begin with first finding out what students believe about the topic before instruction.

Measuring prior knowledge with Conceptual Inventories

Conceptual Inventories (CIs) are designed to identify critical, common misconceptions among students. These can be administered in large lectures and tend to be multiple choice, with choices based on the more common misunderstandings about a topic. CIs can be administered again after misconceptions have been addressed to determine whether there has been conceptual change.

Many of these measures have undergone validation studies and can be generalizable. A list of CIs by discipline is provided below. Many of the CIs are already available for you to use, while others may require permission from the author before using.

It is important to understand that CIs do not include all the possible misconceptions that students may have about a topic. In addition, students can answer correctly on the CI without understanding why it is so. It is recommended to use other formative assessments in conjunction with CIs.