On Theories, Hypotheses, Variables, Validity, and Reliability

Theories and Hypotheses What is (a) “theory”? On Hypotheses: – They usually concern connections among “variables”; – Concern causal relationships, attributes, and comparisons; – Should be testable and falsifiable

Testing a Hypothesis Step 1: A One-Off Test: X ➔ Y? Step 2: Make Multiple Observations in the same setting: –X➔Y1?–X➔Y1? –X➔Y2?–X➔Y2? –X➔Y3?–X➔Y3? …and so on.

Testing a Hypothesis Step 3: Multiple Observations in Dissimilar Settings Step 4: Multiple Observations in Dissimilar Settings, Testing Competing Hypotheses Step 5: Performing a “Crucial Experiment” to decide among Competing Hypotheses

Testing a Hypothesis An additional issue is the possible role of third (or other) variables in the posited relationship. The “Spurious” Relationship: A Third Variable is really the Explanatory One: Z ↓ X →Y The Intervening Variable: X precedes Y but does not cause Y directly: X→Z→Y

Validity and Reliability Validity: Are you measuring/studying what you CLAIM to be? – Face: Does the measure seem reasonable? – Construct: Is the construct used appropriate for addressing the concept that you want to measure? – Predictive: Does the measure have predictive capacity, if that’s desired? – Content: Does the measure include all relevant content that defines it? – Internal: Has you study been designed with enough control to ensure that the causal relationships discovered are real? – External: Has your study been designed to allow its findings to have relevance outside of the study site? – The problem with maintaining internal and external validity concurrently: control versus “realness.” Reliability: Are your findings repeatable? Some valid studies are not very reliable; some reliable measures are not very valid.