Validity versus Reliability

As June approaches, teachers are scrambling to complete those aspects of the curriculum that they haven’t covered yet. As well, many teachers are getting into the mode of assessments. Assessing not only what our students have learned over the year, but esentailly assessing how we as teachers conveyed integrated the information we wished to impart.

Here in the great white, oil producing province of Alberta, many of our grade 3, 6, 9 and 12 student are preparing to write the government achievement and diploma exams. We have all heard the arguments surrounding assessments and the validity and reliabilty of these standardized assessments. Being in a position where every element of my students are assessed at one point or another, I thought I would provide some information as to what teachers should look for in an assessment in terms of reliability and validity.

By definition:

Reliability is the degree by which a test can be counted upon over time. While, validity is the degree to which a test does what it claims to be able to do.

The easiest way to put what I have learned is that:

High reliability does not necessarily equal high validity
High validity almost always equals high reliability.

Metaphorically, this means that the Train engine drives the validity reliability railroad. Attached to the engine (validity) is the coal car(reliability). The coal car could not drive the railway. I hope that it makes sense.

What I have also come to understand over my short career in education is that government standardized tests are snap shots in time, they are only testing what a student knows or remembers during that test, during that day. It should not be necessarily used to determine a students ability, achievement or progess. Governments should use the information gather to determine elements such as curriculum and revisions.

Yes, there is a comparitive aspect to every assessment using information to calculate where a student is in relation to his peers, but as stated in a previous Blog, the BEST group test is only as good as the worst individaul test. This is because many group assessments, also previously stated are simply reading tests, that do not take into account many elements such as SES.

I suppose what I am trying to emphasise is that when giving, or interpreting an assessment, take a carefull look at the assessment, and determine if what the test was testing and whether the test is relating what you are looking for. Also, more importantly an assessment should never determine the education of a child, but the starting point to spring board from.


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