A test is the word we use to talk about “can we find out what is happening here, using what we already know? A test is an experiment, based on lots of previous experience.
You might test your reflexes. To do this, you need to have some idea what a reflex is, what you and people your age usually experience, and what some standard ways of measuring reflexes might be.
An Olympic 100m sprint race is a test. We know that it has taken a human male around 9 seconds to run 100 meters in the past. We know this because we have measured out 100 meters, put a group of people at one end, told them to run as fast as they can to the other end, and used a stopwatch to measure how long it takes them.
Tests are all around us. How cold is your fridge? How empty is your car’s fuel tank? How tall has your hedge grown?
For a test to tell us anything useful, we need to be measuring something that might have changed. We measure how tall a child is because we expect them to grow taller with age. We measure how heavy our pet cat is, because we want to know if we are feeding them too much.
For many tests, we use measures of length, weight, counting something, or timing. We are all likely to have measured something – our weight!
But, what does it MEAN? Why is our weight important? Why bother with measuring it more than once, at birth?
This is where we get into ideas around things changing, or staying the same, or being compared with other things. So, if I weigh 84.3 kg on Friday morning, and 86.1 kg on Monday morning, I might think that I ate and drank a lot over the weekend. I also might think about what other people my height and age could weigh. Is it normal to weigh 86.1 kg? How does that compare with other people my age? Is it normal to weigh 86.1 kg, when I measure at 180 cm tall? What about if I measure at 160 cm tall? What about if I am 7 years old, and weight 84.1 kg? Would that be normal?
By now you might be wondering what the point is? Here it is: when we have a standard way to measure something, and we measure that thing often enough, we can see a pattern. This is true for people’s height and weight with age, it is true for how fast people can run, and true for how often and how long people need to sleep.
When we have enough measurements, we can then start to predict and explain. I now know that being 180 cm tall and 86.1 kg heavy means that I am too big to be a jockey, because the typical jockey is 157 cm tall and weighs around 50 kg.
We can apply this same measure, predict, and explain to anything we can observe. This include correct answers in a spelling test, or how fast you can say the alphabet. We can explain the spelling test score by thinking about how well other children that age do on that test, or on how many times that child has been tested on those words, or on whether the words are even in a language that child can speak. All these factors might influence how we explain the score on a spelling test.
We call tests that measure observed behaviour, but explain the behaviour using psychology “psychometrics” – literally means “to measure something psychological”. So, as soon as we measure speed of answering times tables questions, we are using a psychometric. We are counting how many correct answers are given within a certain time. But, we interpret that score by talking about practice, or learning, or memory, or attention, or all sorts of other things. We don’t really care how many were correct, we care that there were more today than yesterday. We care the practicing we do can show a measurable improvement. We care that it matters if we try harder.
This is the very real point of any psychometric assessment. It tells us information that we care about, by measuring something we can observe, and interpreting the results of those measurements against something that matters to us. This is almost always to answer one of two questions
“How well did I do compared with other people my age?” or “How well did I do compared with the last time I tested myself?”
No point weighing myself unless I can feel good about being in better health than the “Average” person my age or unless I can feel good about not having that any beers over the weekend.
