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Key Takeaways
- Reliability in measurement is about consistency. Validity in measurement is about social agreement.
- Internal validity means that the experiment actually tests what it seeks to test, while external validity means that the study is generic to other situations and contexts.
- A variable refers to a grouping of several characteristics. Attributes are those characteristics.
- Nominal level of measurement has attributes that meet the criteria of exhaustiveness and mutual exclusivity. Ordinal level measurement can be rank ordered, though we cannot calculate a mathematical distance between those attributes. Interval level measurement meets all criteria if the two preceding levels plus the distance between attributes is known to be equal. Ratio level measurement has attributes that are mutually exclusive and exhaustive, can be rank ordered, have an equal distance between them, and have a true zero point.
- Unit of analysis is the entity that you wish to be able to say something about at the end of your study, probably what you’d consider to be the main focus of your study. A unit of observation is the item (or items) that you actually observe, measure, or collect in the course of trying to learn something about your unit of analysis.
- An independent variable is one that causes another. It is the variable that is manipulated by the researcher in order to measure the difference in the outcome or the dependent variable.
- A dependent variable is one that is caused by another.
- An extraneous variable may compete with the independent variable in explaining the outcome.
- A rival plausible explanation (RPE) is an alternative factor, to the idea that you might have been expecting respondents to try to answer, that may account for the results you observed in your research.
