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Content validity

2 min read

This work by Nevit Dilmen is licensed under a Creative Commons Attribution-Share Alike 3.0 Unported Licence.

This week we turn to validity. It can be a tricky concept and in fact was something that took me some time to 'get' at first. The easiest approach I've found to interpreting 'validity' is to ask the question: does the test measure what it's supposed to measure?

What do we want it to measure? Do we know what we want to measure, in the first place? So often I think we plan assessment without being perfectly clear about our purpose. (Sometimes it's because our learning outcomes aren't very clear to begin with.) Brown and Abeywickrama (2010) list other qualities of a valid test but I think the above definition is enough to work with for now.

Following the same book, I'm starting with content-related validity. This is pretty straightforward: is what you want to test in the test? This might seem kind of 'duh' but it's actually a trap that's quite easy to fall into. For instance, our purpose might be to test learners' grammatical accuracy when speaking, but instead of actually getting them to speak, we set an MCQ grammar test. The former would be a direct test, while the latter (arguably) an indirect test of the same thing. Indirect tests are often used for reasons of practicality and reliability; obviously it's much easier to mark a class's MCQ test (it could even be done automatically) than to administer an individual oral test for each student.

If it really isn't possible to achieve high content validity, then we've got to look into the other validities of our test. More of those in the coming weeks. In the meantime, keep your questions and comments coming with on Twitter.