PSYC 2300 Lecture Notes - Lecture 3: Beck Depression Inventory, Validity, Operational Definition

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8 Feb 2018
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Defining and Measuring Variables
1. Defining Variables
a. Defining variables (conceptual definitions)
i. Variations in definitions
b. Hypothetical constructs: theoretical attributes/mechanisms that help
explain/predict behavior
i. May not be directly observed (e.g. IQ, hunger, motivation, anxiety)
ii. IQ a’t e eighted or easured phsiall, ut oserale ehaiors
are associated with IQ
2. Operationalizing Variables
a. Operational definition: specific steps for measuring a construct (measurement
procedure)how do we measure this?
b. Specificif unclear, difficult to evaluate whether data supports hypothesis
c. Reliably, consistently, measured
d. Validly, accurately measured
e. Many ways to operationalize variables
i. The more ways you can operationalize in one study, the better
f. Limitations
i. Not the same as actual constructthe more we operationalize, the more
we move away from the construct
3. Hypotheses and constructs
a. Conceptual hypotheses: prediction about relation(s) between two or more
general concepts; very broad
i. E.g. exercise produces weight loss
b. Operational hypotheses: specific predictions about relations between two or
more precisely defined concepts
i. E.g. hat eatl do e ea  eerise?—1/2 hr aerobic activity, 5
days/week, where heart rate is less than 140 bpm will result in weight
content validityreduction, BMI reduction, and a decrease in weight and
clothing size
4. Measurement modalities
a. 3 common modalities and limitations
i. Self-reports (SR)scales, survey, questionnaire or paper-pencil measure
1. Problempeople may over and underreport
ii. Physiological measures (PM)e.g. heart rate
1. Doable, but you need the right equipment and human consent
iii. Behavior measures (BM)e.g. observe through one-way mirror
1. Doable, but behavior may be situational and may represent only a
portion of the entire construct
5. Validity
a. Accuracy of resultsmeasures what it purports to measure
b. Types
i. Face validity—does the easure appear to easure hat it’s iteded to
measure?
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