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How to Know if a Quantitative Research

Design Is Appropriate for Your Thesis

Taken from: Wiersma, W. & Jurs, S.G. (2009). Research methods in education: An introduction (9th ed.). Boston, MA: Allyn and Bacon

Characteristics of Quantitative Research

•  Deductive •  Look for relationships, effects, causes •  Theory-based •  Focused on individual variables •  Context- free (Generalizations) •  Detached role of researcher •  Statistical analysis

(Wiersma  &  Jurs,  2009,  p.  15)  

When to Choose Quantitative Research

If you are interested in:

•  Determining relationships, effects, and/or causes

•  Testing theories, models, approaches (even if that is not an explicit goal of the study, but theoretical principles are important in one way or another)

Types of Quantitative Research Designs

•  Pre-experimental: Little or no control

•  Experimental: High degree of control

•  Quasi-experimental: Minor level of control because random selection or assignment is not possible. Statistics is used to improve the control of variables

Pre-Experimental Designs

•  Case study •  One group pretest –

posttest •  Static group comparison or

cross-sectional

Case Study Design

•  Description: One group is studied after applying a treatment or intervention

•  Diagram: X O2 X = Treatment O2 = Posttest

•  Threats to validity: Little or no control of the effect of variables, history, maturation, selection, mortality, and interaction effects of selection biases and the experimental treatment

 

One Group Pretest-Posttest Design

•  Description: The dependent variable is measured, the treatment or intervention is applied, and the dependent variable is measured again

•  Diagram: O1 X O2 O1 = Pretest X = Treatment O2 = Posttest   •   Threats to validity: History, maturation,

instrumentation, mortality, selection- maturation interaction, reactive effect of testing, and interaction effects of selection biases and the experimental treatment

Static Group Comparison or Cross- Sectional Design

•  Description: A group to which a treatment has been applied is compared to another group that has not experienced it

•  Diagram: X O2 X = Treatment O2 = Posttest                  -­‐-­‐      O2

•   Threats to validity: Selection, mortality, reactive effect of testing, and interaction effects of selection biases and the experimental treatment

Experimental Designs

•  Randomized posttest groups •  Pretest- posttest control group •  Solomon four groups •  Factorial

•  Descrip(on:  Two  groups  are  compared  using  pos@est  and  random  assignment  of  subjects  and  treatment  to  control  prior  differences  

•  Diagram:        R      X      O2        R = Randomization X = Treatment O2 = Posttest

                   R      -­‐        O2  

•  Threats  to  validity:  The  change  of  the  experimental  group  cannot  be  measured  

 Randomized Posttest Groups Design

•  Description: Two groups are compared using pretest and posttest and random assignment of subjects and treatment

•  Diagram: R O1 X O2 R = Randomization O1 = Pretest X = Treatment O2 = Posttest

R O1 - O2

•  Threats to validity: Reactive effect of testing

 Pretest –Posttest Control Group Design

•  Description: To address the reactive effect of testing, two control groups are added to the pretest-posttest control group design; one without taking pretest and another one without pretest and treatment

•  Diagram: R O1 X O2 R O1 - O2

R - X O2

R - - O2 R = Randomization O1 = Pretest X = Treatment O2 = Posttest •  Threats to validity: None by itself

 Solomon Four Groups Design

•  Descrip(on:  The  different  levels  of  two  or  more  independent  variables  (factors)  are  considered  to  establish  not  only  their  effects  on  the  dependent  variable  but  also  the  ones  caused  by  the  interacMon  among  them  

•  Diagram: R X11 O (Notation of a 2 X 2 factorial design) R X12 O

R X21 O

R X22 O  R = Randomization X11 = Factor 1, level 1 X12 = Factor 1, level 2 X21 = Factor 2, level 1 X22 = Factor 2, level 2 O = Measurement

 •  Threats  to  validity:  None  by  itself  

Factorial Design

Quasi-Experimental Designs

•  Nonrandomized pretest-posttest control group •  Counterbalanced •  Time series

•  Description: Two groups are compared using pretest and posttest. There is not random assignment of subjects since they are already in groups

•  Diagram: O1 X O2 O1 = Pretest X = Treatment O2 = Posttest

O1 - O2 •  Threats to validity: Selection, statistical regression,

and reactive effect of testing

 Non Randomized Pretest –Posttest Control Group Design

•  Description: The order in which treatments are administrated is changed during the study so as to test every subject for all the considered conditions

•  Basic Diagram : G1 XA XB O

G2 XB XA O

X = Treatment G = Group O = Measurement

•  Threats to validity: Multiple treatment interference

 Counterbalanced Design

•  Description: The dependent variable is measured

several times before applying a treatment and then a

new series of measurement is performed

•  Diagram : O1 O2 … X Oi… On

X = Treatment O = Measurement

•  Threats to validity: History and reactive effect of

testing

 Time Series Design

Now you know: Any question?

1.   Characteristics of quantitative research

2.   When to choose quantitative research

3.   Types of quantitative research designs

4.   Description, basic diagram, and threats to validity of each type of design

 

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