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Variables. Independent Variable An independent variable is one that an investigator manipulates to determine its effect. Independent variables seem to have a causative effect upon other variables. Dependent Variable
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Variables • Independent Variable • An independent variable is one that an investigator manipulates to determine its effect. • Independent variables seem to have a causative effect upon other variables. • Dependent Variable • Variations in dependent variables are assumed to depend on or be caused by another variable.
Dependent or Independent? • Using the Coke versus Pepsi experiment in the way it was intended to be conducted, what was the dependent variable and what was the independent variable? • If the temperature of the drink really determined the outcome, what type of variable would temperature be in the study?
Levels of Measurement of Variables • Nominal • This level is good for identifying categories. • Ordinal • In this level categories have an order and this order is significant, common with rankings. • Interval • At this level variables are ranked using numbers and the distances between the numbers have a real meaning. • Ratio • In this level an interval variable has a meaningful zero point.
Validity Versus Reliability • Validity: Are you measuring what you are supposed to be measuring? • Reliability: Are you measuring consistently?
Internal Validity • Internal validity is the extent to which observed differences on the dependent variable are attributed to the independent variable and not to some confounding variables. • The key to internal validity is whether or not subjects can be randomly assigned to various levels of the independent variable.
External Validity • External validity is the extent to which the results of the study can be generalized elsewhere. You make generalizations about a population, is the sample representative of the population?
Content Validity • Content validity is the degree to which a test measures an intended content area.
Reliability • Reliability is the degree to which a test consistently measures whatever it measures. • This is the group to which the researcher would like the sample results of a study to be generalizable.
Sample • A sample is a number of individuals selected from a population for a study, preferably in such a way that they represent the larger group from which they were selected.
Research Study Information • Purpose of study • Problem statement/research questions • Assumptions & limitations • Rationale/significance • Research methodology - general method, data collection and analysis • Major findings and conclusions
Research Ethics • As a researcher, you have certain ethics you need to uphold. • Some of your responsibilities include protecting participants from harm, adhering to promises made to participants, etc.
The Institutional Review Boards • The Institutional Review Board at an institution engaged in research must review and approve research if it involves use of human subjects. • The Institutional Review Board for the Protection of the Human Subjects (IRB) is the regulatory body of IUP that is responsible for the review of research that involves human participants.