So, is a randomised test fair?

It depends.

A randomised test can be totally fair but it can also be biased.

A test is biased when the results have consequences that unfairly advantage or disadvantage test takers.

Is it possible to determine whether a test is fair? Whether it is equally difficult for all candidates?

Yes it is. But only in hindsight.

An analysis of the average p-value of the test is of great help in establishing the fairness of the test. When the average p-values ​​are spread across a broad range then it is highly likely that several tests had varying levels of difficulty.


But…in hindsight is too late!

You want certainty about the fairness of your test before it is delivered to your candidates.

It will prevent you from having to deal with some considerable headaches afterwards 🙂 .

So, how is this done?

How does one create a test that is fair to each and every candidate?

The key condition is that you have a clear understanding of the level of knowledge and/or skills of your candidates.

Your candidates really do not have to know the answers to all of the questions. In fact, some things are learnt by doing and through gaining experience.

So what does this have to do with randomised tests?


Because: When designing a randomised test you want to ensure that candidates who come well prepared are presented with questions that they can answer.

You want to be able to distinguish the competent candidates from those that require some further education. Evidently, you work your way back starting from the norm.

So what is the goal? What do you want to measure?

You want to be able to assess a candidate’s knowledge and insight at a predetermined level of the subject matter. You want to set a standard. And for this to work correctly you need to be a subject matter expert. You apply your knowledge of the subject matter during an item review and qualify all of the items into buckets of easy, moderate and hard questions. This method of standard setting is the foundation for a good randomised test. This approach is known as the Method of Angoff.

Depending on the testing solution that you use you ensure that all levels of difficulty are reflected in your test specifications matrix – or blueprint. QuestionMarkPerception has this to say on the subject.

Seeding items

Andriessen’s Sisto offers the possibility of seeding pretest items. These items do not count towards a candidate’s final score but you can use them for determining their p- and rit-values. Is it a hard, moderate or easy question.

When you have collected sufficient information about the pretest item you then decide whether it can be included in the test. This allows you to remove an item that is not performing well or you amend it and include it as a new pretest item in the next release of your test.

Taking this approach to the design and further development of your test allows you to improve its quality.

Your item bank will increasingly reflect items of a similar difficulty level.

Should you wish to use items with significantly different levels of difficulty then you will want to label your items or use a test matrix that is designed to fairly distribute these items.

Randomised tests: The advantages:

  1. They decrease the value of exam or item theft. Every test is different!
  2. It is easy to swap pretest items in and out.
  3. It allows you to gradually grow your item bank increasing the randomisation of items.
  4. Every candidate is presented with a test that is unique.

So, is a randomised test fair?


But it requires work and maintenance. Particularly in the area of item difficulty.

Consider this: video clips in tests

One of the advantages of computer based testing is the ability to use multimedia files.

From a technical perspective the inclusion of video clips is not a problem. Almost all vendors of computer based testing solutions will offer this in some shape or form. There is a variety of low-cost tools that will allow you to place your videos online and embed them your test.

video in test

YouTube offers a simple, reliable and cost-efficient way of embedding video in your test.

By default YouTube videos are public, which means that anyone can watch them.

Keep this in mind when you include video in a test.

The use of video complements the candidate experience and it can add flavour to formative tests. In regards to summative tests you want to be more careful. It is important to establish that candidates who have already seen the video before the test have no advantage over those who haven’t.


YouTube offers the option of making a video unlisted.

This means that only those people that have the link to the video can view it. Unlisted videos don’t show up in YouTube’s search results unless someone adds your unlisted video to a public playlist.

A good alternative to YouTube is Vimeo. Vimeo Plus or Pro subscriptions are very affordable (approximately $60 or $200 per year respectively) and offer features such as video password protection, domain-level privacy and advanced views statistics. Furthermore you can add your own logo to the video player – a nice touch!

Consider this when using (online) video:

  1. What is the impact if a candidate has already watched the video before the start of the test?
  2. Do you have the rights to use the video in your test?
  3. Is the bandwidth sufficient for all candidates to view the video simultaneously?
  4. Can YouTube, Vimeo or another video player be accessed from the test station?

Sources: and

Example of embedded video in the English Example.