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Lecture 4

Lecture 4 - Definition & Levels.docx

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Western University
Psychology 2800E
Doug Hazlewood

Definition & Levels Prologue: Background Review  Concepts are words (can’t be directly observed; aka constructs; must be translated into things that can be observed)  Operational definitions describe how concepts will be “measured” (or “manipulated”)  We’ll talk about manipulating concepts when we discuss experiments  Skim chapter 5 W&M discussion of independent, dependent, subject, & confounded variables (p. 120-122) – not tested right now though  Skip ‘nuts and bolts’ (134-135); case in point & reading between the lines (137); and exercises 5.2-5.10 Part 1: Definitions  Measurement: using rules to assign values to variables  Values can be numbers or names  Variable: any observable attribute of a concept that has more than one value  Biological sex is a concept with observable attributes; with two basic values: male & female  An exam grade is a concept that has observable attributes; from 0%-100% correct Part 2: Types of Variables A. Categorical variables (values identify distinct “categories” of things)  Values can be names (e.g., males, females)  Values can be numbers (e.g. males assigned a value of 1 and females assigned a value of 2)  Necessary when analyzing data (SPSS) - > converts words back to numbers  Number don’t have numerical meaning (don’t tell us about “quantity”) -> like symbols  Numbers can be used to identify individuals within categories (e.g., SIN, student #) B. Quantitative Variables (values are numbers that represent quantity; e.g., exam grades).  Can be:  Continuous: values represent quantity with no gaps between values (e.g. height; weight)  Discrete: have gaps between values (e.g., can get 70 or 71 answers correct on MC exam, but not 70.5)  Values can be words (e.g., “high” vs “low”; represent quantity: low = 1; high =2) C. Measurement involves using rules to assign values to variables Part 3: Levels of Measurement (and Measurement Scales) A. Nominal scales (name categories of things)  Information: observations are “same” or “different” (equal or no equal)  Rule: Same things get same nominal value; different things get different nominal value  Note:  “Categorical” variables are always nominal;  Values can be names or numbers (numbers don’t indicate “quantity”), BUT  You can count the number of things in each category B. Ordinal Scales (provide “quantitative” info)  Information: Same-different PLUS more-less (rank-order or relative magnitude)  Rule: Rank order of scale values must represent rank-order of magnitudes on dimension being measured  Example: Performance in race (fastest is ranked 1; next fastest is ranked 2…)  Problem: Ordinal scales don’t specify the distance between scale values (“size of intervals”) C. Interval Scales  Information: Same- different; more-less; PLUS
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