Child Development 133 
Research Methods in Human Development

Sections 01 & 05
Hembree            Fall, 2012

 

Variability and Variance

I. Overview of Research Approaches:

A. Descriptive/Qualitative

 

 

 

B. Experimental

 

 

 

C. Correlational

 

 

 

 

D. Quasi-experimental

 

 

 

 

E. Developmental

 

 

 

 

 

II. Variability, Variables, and Variance

A. Behavioral Variability 

Behavior varies (changes)

  • across situations

 

  • among individuals

 

  • over time

 

B. Variables

e.g., activity level

1. Independent/Dependent variables

types of IVs:

  • physiological (altering biological state)

 

 

  • experience (effects of previous training or learning)

 

 

  • stimulus (environmental)

 

 

  • participant characteristics (sex, age) 

 

 

 

 2. Extraneous and nuisance variables

 

 

 

 

 

C. Research and behavioral variability

1.  All research questions concern behavioral variability 

 

 

 

2.  Good research allows us to unambiguously explain behavioral variability

 

 

 

3.  Good research allows us to measure behavioral variability well

 

 

 

4.  Statistics are used to summarize and account for behavioral variability (descriptive vs. Inferential statistics)

 

 

 

    D. Variance

1.  an index of behavioral variability

 

2. a statistic used to describe how much something varies (s2)


s2= Σ(X-X)2
           N-1

 e.g., activity level 

 

X

X-X

(X-X)2

X=3.0 

2

2-3 = -1

1

 

2

2-3 = -1

1

 

3

3-3 = 0

0

 

3

3-3 = 0

0

 

5

5-3 = 2

4

 

Σ= 15

 

Σ = 6

s2 = 6/4 = 1.5

 

 

E.  Explaining variance

   1. Problem of identifying effects through “noise”

 

 

 

    2. Systematic vs. Unsystematic (random) variance

 

 

 

 

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Send problems, comments or suggestions to: hembrees@csus.edu

California State University, Sacramento
College of Education
Department of Child Development

Updated: August, 2012