Inter-rater reliability ensure that judges evaluate subjects in same manner on a testing scale. Low internal reliability tells you that there is more than one construct that you"re measuring. A factor analysis will inter-correlate different items to see how well they correlate together. You would expect that items that measure the same construct will have a high correlation, however low correlation will indicate that there is more than one construct. A reliable measure is useless if it is not valid. Does my measure cover all of the concepts of my construct? assessing whether your measure (items in a survey) includes all components of the operational definition of the abstract concept. Content validity refers to the extent to which your measure captures all parts of a define construct. For example, intelligence has a whole host of factors associated with it such as, the ability to reason, plan, think abstractly, comprehend complex ideas, learn quickly, etc.