I n t o t o R e s e a r c h D e s i g n & A n a l y s i s |Chapter 3Variables are the core unit of psychological research.Variable: something that varies; has at least 2 levels/valuesConstant: something that could potentially vary but that has only one level in the studyin questionResearcher in any study either measure or manipulate each variableMeasured Variable: one whose levels are simply observed and recordedManipulated Variable: a variable a researcher controls, usually by assigning participants to the different levels of that variableConceptual Variables: abstract concepts such as “shyness” or “intelligence”; sometimes called ConstructConceptual Definitions: conceptual variables that are carefully defined at a theoretical levelOperational Definitions: Operational Variables; Operationalizations; the empirical research from testing hypothesesOperationalize: to turn a concept of interest into a measured or manipulated variableThree ClaimsClaim: the argument someone is trying to makeFrequency Claim: describe a particular rate or degree of a single variable {the percentage of a variable, the number of people who engage in some activity or a certain group’s level on a variable},- Focus on one variable- Always measured, not manipulatedAssociation Claims: argues that one level of a variable is likely to be associated with aparticular level of another variable- Must involve at least two variables- Variables are measured, not manipulated3 types: - positive association: when high goes with high and low goes with low- uses scatterplots- positive slope- negative association: high goes with low and low goes with high- uses scatter plots- negative slope- zero association: no association between the variables; zero correlation- no slopeCasual Claim: arguing that one of the variables is responsible for changing the otherI n t o t o R e s e a r c h D e s i g n & A n a l y s i s |Chapter 3A casual claim that contains tentative language- could, may, seem, suggest, sometimes, potentially- is still a casual claimValidity: the appropriateness of a conclusion or decision, and in general, a valid claim isreasonable, accurate, and justifiableConstruct Validity: how well a conceptual variable operationalizedWhen you ask how well a study measured or manipulated a variable, you are interrogating the construct validity: how accurately a researcher has operationalized each variableExternal Validity: how well the results of a study generalize to, or represent, people contexts besides those in the study itselfStatistical Validity: Statistical Conclusion Validity, is the extent to which a study’s statistical conclusions are accurate and reasonable; questions will vary depending on the claim2 kinds of mistakes:- A study might mistakenly conclude, based on the results from a sample of people, that there is an association between 2 variables when there really is no association in the real populationType I Error: false positive; increase the chances that they will find associations only when they are really there- A study might mistakenly conclude from a sample that there is no association between 2 variables when there really is an association in the full populationType II Error: miss; reduce the chances that they will miss associations that are really thereCorrelation Study: a study that measures two or more variablesI n t o t o R e s e a r c h D e s i g n & A n a l y s i s |Chapter 3Covariance: the first criterion a study must satisfy in order to establish a casual claim.A study must satisfy two additional criteria to justify the use of causal language: temporal precedence and internal validityTemporal Precedence: it comes first in time, before the other variableInternal Validity: the third-variable criterion, a study should be able to eliminate alternative explanations for the association; alternate explanationsExperiment: one variable is manipulated and the other is measuredIndependent Variable: the manipulated variableDependent Variable: the measured variableA study can support a causal claim only if the research behind it shoes covariance, and only if the variables were studied in a way that ensures both temporal precedence and internal validity.Internal Validity is only important for interrogating a causal claim.Indeed, each validity addresses a different aspect of a study: The evidence it provides for a causal statement, the measurements used, the study’s generalizability, and the statistical accuracy of its conclusions.Asking questions about each validity in turn is a good way to make sure you have considered all the important aspects of the study’s