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.
Trajectory Modeling (Group-Based)
Group-based trajectory modeling is used to identify subgroups within a population that follow distinctive developmental trajectories. For example, within a cohort of young children there may be three such groups with different math achievement trajectories from kindergarten through grade 5: (1) accelerated growth in achievement; (2) steady growth in achievement; (3) declining growth in achievement.
Treatment Effect
Change in the outcome variable that is due to some intervention. Sometimes used to describe the change in an outcome variable that is due to changes in the independent (predictor) variable, even if the independent variable is not an intervention.
Treatment Offered
In experimental research, individuals or groups of individuals are randomly assigned to a treatment (intervention) or control group. Those assigned to the treatment group are offered the opportunity to participate in the treatment and those assigned to the control group are not. Intent-to-treat analyses assess the effect of being offered the treatment, while treatment-on-the treated analyses assess the effect of participating in the treatment.
Treatment-on-the-Treated
Treatment-on-the-treated (TOT) is an estimate of the effect of a treatment or intervention on those who received the treatment regardless of their original assignment to treatment or control groups.
Triangulation of Data
Using of a variety of research methods or sources to collect data pertaining to a specific research problem or question. This process helps to enhance the validity of data since it does not overly rely on any particular method. It can also result in a more comprehensive understanding of the phenomenon under study.
Two-Tailed Test
A type of test that is used when a researcher is unsure of whether the independent (predictor) variable has a positive or negative effect on the dependent (outcome) variable, or whether the mean for group A is greater than or less than the mean for group B. A two-tailed test is also used when comparing the mean for a sample to a given value of x, when the mean can be either greater than or less than x. By contrast, a one-tailed test will test either that the mean is significantly greater than x or that the mean is significantly less than x, but not both.
Two-Way ANOVA
A statistical test to study the effect of two categorical independent variables on a continuous outcome variable. Two-way ANOVAs analyze the direct effect of the independent variables on the outcome, as well as the interaction of the independent variables on the outcome.
Type I Error
An error that occurs when a researcher concludes that a statistically significant difference between two groups or the relationship between two variables exists (based on the analysis of the sample), when in fact the difference or relationship does not exist in the population from which the sample was selected (null hypothesis is true). The amount of risk of a Type I Error a researcher is willing to accept is decided upon prior to analyzing the data. This probability of a Type I Error is also called a significance level.
Type II Error
An error that occurs when a researcher concludes that no significant relationship between two variables (based on analysis of sample data) when in fact the relationship does exist in the population from which the sample was drawn. The probability of not making a type II error is also called the power of a statistical test.
Typology
A descriptive, categorical scheme that may serve as the foundation for data coding or data analysis in a qualitative study. he types or categories comprising a typology should be mutually exclusive--separate and distinct with no overlap--and exhaustive--all the data must fall into some category.