(https://www.yourwebsite.com/test-validity-and-reliability-whats-the-difference)

When it comes to measurements, we often focus on hard data such as weight, temperature, and pH. However, determining validity is just as important as accuracy in these types of measurements. In fact, even if the conditions change – whether you're aware of them or not – your test results should be different.

But what does validity mean? Simply put, it's the measure of whether a test is accurate. A valid test result doesn't necessarily have to be consistent; as long as it's accurate, that's all that matters. For example, if you have a ten-pound weight and your scale reads it as ten pounds, then the measurement is valid.

On the other hand, reliability refers to whether your tests produce consistent results under the same conditions. If your radar gun isn't properly calibrated, it may register 50 mph for every car that goes by at 35 mph – this is neither reliable nor correct. A tool can have reliable measurements that aren't valid, but test results can't be valid if they aren't reliable.

There are four major types of determinations of reliability: test-retest, inter-rater, parallel forms, and internal consistency. Meanwhile, there are three major types of determinations of validity: criterion, content, and construct.

Ideally, you want your equipment to produce both reliable and valid results – or consistent and accurate measurements. In the context of research, testing, and statistical analysis, understanding the difference between validity and reliability is crucial.

In summary, validity refers to accuracy in measurements, while reliability determines consistency. Both are used to determine how well a test measures something, but they tell you different things about your test. By recognizing the importance of both validity and reliability, you can ensure that your tests provide accurate and reliable results.

Test validity and reliability