The research glossary defines terms used in conducting social science and policy research, for example those describing methods, measurements, statistical procedures, and other aspects of research; the child care glossary defines terms used to describe aspects of child care and early education practice and policy.
Intercept
The expected value of a dependent variable when all the independent variables are equal to zero.
Intercept
In regression analysis, the predicted value of Y (dependent variable) when all X variables (independent variables) are zero (0). It is also called the Y-intercept or the constant term. It is the place where the regression line crosses the Y-axis.
Internal Validity
The extent to which researchers provide compelling evidence that the causal (independent) variable causes changes in the outcome (dependent) variable. To do this, researchers must rule other potential explanations for the changes in the outcome variable.
Interval Scale
A scale of measurement where the distance between any two adjacent units of measurement is the same but the zero point is arbitrary. Scores on an interval scale can be added and subtracted but cannot be meaningfully multiplied or divided.
Interval Variable
A variable wherein the distance between units is the same but the zero point is arbitrary.
Intervening Variable
An intervening variable or mediating variable is something that effects or helps to explain the relationship between an independent and a dependent variable. An intervening variable is the link between an independent and a dependent variable. It is predicted by the independent variable, and it predicts the dependent variable. In early childhood research, intervening variables are often used to identify the processes that underlie the relationships between independent variables and dependent variables. For example, the time parents spent reading to children may explain the relationship between parental education and children's reading scores on a standardized test.
Intervention
The situation or variable introduced to affect the dependent variable (outcome); manipulations of the subject or the subject's environment performed for research purposes. In early education, interventions often involve the introduction and use of one or more instructional approaches designed to improve children's learning. Other interventions might include professional development training designed to improve the quality of teaching in the classroom and ultimately children's learning.
Interviewer Error
A type of non-sampling error caused by mistakes made by the interviewer. These may include influencing the respondent in some way, asking questions in the wrong order, or using slightly different phrasing (or tone of voice) than other interviewers. It can include intentional errors such as cheating and fraudulent data entry.