Child Development 133 (03, 04,
72, 73 & 74)
Research Methods in Human Development

Hembree            Spring, 2013

 
Variance and Variability

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

 

 

 

 

 

 

 

 

 

 

 

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

California State University, Sacramento

College of Education

Department of Child Development

Updated: January 25, 2013

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