Assessment, Statistics, and Research

  US Presidential Poling Data Reveal A Potential Validity Problem Do you want to know how people are likely to vote? Or, do you want to know who is likely to be the next president? What is the purpose of national polls? Those interested in politics get a glimpse of how people might vote in an election. But how valid are those data?  What is not obvious is that the national polls are not the most valid measure of who will become president. That’s not because of problems of accuracy or methodology. It’s because in the US, the popular vote does not determine who will be the next president. Hence, national polls lack the level of predictive validity available in other polls. Validity refers to how well a measure measures what it is supposed to measure.  Pollsters  assess validity in different ways.  The key question is what is the purpose of the poll?  If the purpose is to reveal the likely votes of Americans, then a national poll has a degree of construct validity. If the poll is to p

  What makes a test valid? is a tricky question.  The short, and rather obnoxious response is, “nothing.”  Like reliability , validity is a property of test scores  rather than tests but more accurately, an interpretation of the scores. But it is important to take the question seriously when test-takers and users are wondering how much confidence to place in a test score. As with many aspects of science, the answers can be simply stated but there is a complicated backstory. Validity Traditions For many, the traditional views of test score validity will be sufficient. Tests measure constructs. Scientific constructs are ideas that have features that can be measured like reading comprehension, dominance, short-term memory, and verbal intelligence. Construct validity is not a single entity but rather the current state of knowledge about how a test instrument’s scores have functioned in many settings and in relation to criteria. Construct vali