Validity in experimental design: the way in which participants are allocated to a study’s condition may affect the validity of what is found. Validity in sampling methods: if there is an error in the sampling method then the results of the research will not accurately reflect the target population and this will mean that there is a problem with the study’s external validity. Therefore, it is vital that a research study is designed in a way that will not affect either internal or external validity. A study which focused on men would not be valid as it is not measuring what it sets out to measure – it would be seen to lack external validity. If the same research were looking at body language amongst women then they are the target population. For example, if a study was set up to measure how much people communicate via body language, then the way in which the research is set up must ensure that it is body language which is being tested this is known as internal validity. Validity refers to the extent to which research measures what it has actually set out to measure. Experts(in this case, math teachers), would have to evaluate the content validity by comparing the test to the learning objectives.Validity is different to reliability and you will need to be able to clearly differentiate between the two. of each question, analyzing whether each one covers the aspects that the test was designed to cover.Ī 4th grade math test would have high content validity if it covered all the skills taught in that grade. 
Assessing content validity is more systematic and relies on expert evaluation. On the other hand, content validity evaluates how well a test represents all the aspects of a topic. When a test has strong face validity, anyone would agree that the test’s questions appear to measure what they are intended to measure.įor example, looking at a 4th grade math test consisting of problems in which students have to add and multiply, most people would agree that it has strong face validity (i.e., it looks like a math test). The difference is that face validity is subjective, and assesses content at surface level. Face validity and content validity are similar in that they both evaluate how suitable the content of a test is.
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