Validity is a measure of how sound the instrument is. A valid instrument is one that measures what it states it measures and does not measure additional variables. Validity also applies to the interpretation. A valid study is one where the findings truly represent the variables you are claiming to measure. Therefore, the interpretations that are made based on the findings are appropriate given the design and method of the study. There are numerous types of validity: criterion, concurrent, ecological, and predictive. Criterion validity compares the test results with the outcome. This is commonly done by correlating the results of one assessment to the results of another assessment. Concurrent validity applies to the creation of a new test. To establish concurrent validity you would measure how well a new test compares to an established test. Ecological validity refers to how generalisable your study’s results are to the real world. Predictive validity tells you how well a test can predict a characteristic of an individual. Reliability and validity are two terms commonly seen together. However, reliability and validity are distinct terms.