Quantitative Research Quantitative Research DesignDesign

An OVERVIEWAn OVERVIEW

Quantitative Research:Quantitative Research:

• Systematic scientific investigation of data and their relationships.

• The kind of research that involves the tallying, manipulation, or systematic aggregation of quantities of data.

(Grant Henning "Quantitative Methods In Language Acquisition Research“)

Quantitative Research:Quantitative Research:

• The collection of numerical data in order to explain, predict and/or control phenomena of interest.

(L.R. Gay ”Educational Research: Competencies for Analysis and Application”)

Quantitative Research:Quantitative Research:

• An inquiry into a social or human problem based on testing a theory composed of variables, measured with numbers, and analyzed with statistical procedures, in order to determine whether the predictive generalizations of the theory hold true.

(John W. Creswell ”Research Design: Qualitative and Quantitative Approaches”)

Overview of Quantitative ResearchOverview of Quantitative Research

• The objective of quantitative research is to develop and employ mathematical models, theories and hypotheses pertaining to natural phenomena.

• Measuring is key in quantitative research because it shows the relationship between data and observation.

Quantitative Research MethodsQuantitative Research Methods

• The basic building blocks of quantitative research are variables.

Variables are something that takes on different values or categories.

Common Types of Variables Classified by Level of Common Types of Variables Classified by Level of Measurement and by Role of VariableMeasurement and by Role of Variable

Variable Type Key Characteristic Example

Level of Measurement

Categorical Variable

Made up of different types or categories of a phenomenon

Gender categories: male and female

Quantitative Variable

Varies in degree or amount of a phenomenon

Annual Income varies from zero income to very high income level

Variable Type Key Characteristic ExampleRole Taken by the Variable

Independent Variable

Presumed to cause changes to occur in another variable (causal variable)

Amount of studying (IV) affects test grades (DV)

Dependent Variable

A variable that changes because of another variable (effect or outcome variable)

Amount of studying (IV) affects test grades (DV)

Mediating Variable(Intervening Variable)

Comes in between other variables, helps to delineate the process through which variables affect one another

Amount of studying (IV) leads to input and organization of knowledge in long-term memory (mediating variable) which affects test grades (DV)

Moderator Variable

Delineates how a relationship of interest changes under different conditions or circumstances

Perhaps the relationship between studying (IV) and test grades (DV) changes according to the different levels of use of a drug such as Retalin (moderator variable)

Types of Quantitative researchTypes of Quantitative research

•EXPERIMENTAL RESEARCH DESIGN

•NONEXPERIMENTAL RESEARCH DESIGN

Experimental Research DesignExperimental Research Design

• The purpose of experimental research is to study cause and effect relationships.

• Its defining characteristic is active manipulation of an independent variable (i.e., it is only in experimental research that “manipulation” is present).

• Also, random assignment (which creates "equivalent" groups) is used in the strongest experimental research designs.

Correlational ResearchCorrelational Research

• To find if the data has an observable relationship that can be further specified in terms of magnitude and/or an increase or decrease.

Characteristics of Correlational Characteristics of Correlational ResearchResearch

• Correlation indicates the strength and direction of a linear relationship between variables.

Correlation and SignificanceCorrelation and Significance

• Is there a relationship between two variables/data?

• What is the direction of the relationship?

• What is the magnitude?

• These relationships may show any tendency for the variables to vary consistently.

• Pearson’s product moment coefficient correlation: -1.0 to +1.0

Ex post factoEx post facto

‘‘from what is done afterwards’from what is done afterwards’

• Studies that investigate possible cause and effect relationships by observing an existing condition or state of affairs and searching back in time for plausible causal factors.

Characteristics of Ex Post FactoCharacteristics of Ex Post Facto

• Researcher takes the effect/dependent variable and examines it retrospectively

• Establishes causes, relationships or associations and their meanings.

• Researcher has little to no control over independent variables.

• Flexible by nature.

When to use this?When to use this?

• You can use this where more powerful experimental designs are not possible; when you are unable to select, control and manipulate the factors necessary to study cause and effect relationships directly, or when control variables except a single independent variable may be unrealistic and artificial.

Ex post facto advantages and Ex post facto advantages and disadvantagesdisadvantages

Advantages• Show a correlation where

more rigorous experimentation is not possible

• Exploratory tool• Useful to avoid articiality

in the research.• Shows cause and effect

relationships

Disadvantages• Lack of control for

independent variable and randomizing subjects.

• Never certain if causative factor has been included or identified

• Relationship between two factors does not est. cause and effect.

• May be regarded as too flexible.

ExperimentalExperimental

• Research in which the investigator deliberately controls and manipulates the independent variable to observe the effect of that change on another the dependent variable.

How and when to useHow and when to useExperimental ResearchExperimental Research

• Most commonly used in Educational research.

• You vary the independent variable and look for the effect it has on the dependent variable.

How and When to use Quasi-How and When to use Quasi-experimental researchexperimental research

• Used when you have control over the “when and the whom of measurement”, but lack control over the “when and to whom of exposure.”

• Common in educational research.

How and when to use Single Case How and when to use Single Case researchresearch

• Process of continuous assessment of some aspect of human behavior over a period of time.

• Involves “intervention effects”, that are replicated in the same subject(s) over time.

• Used in many fields including psychology, education and social work.

How and when to use Meta-How and when to use Meta-analysis researchanalysis research

• Research to explore the effectiveness of classroom methods.

• Involves aggregating the results of other studies into a coherent account.

Useful TermsUseful Terms

• Correlation- Indicates the strength and direction of a linear relationship between two random variables.

• Ex post facto- from the Latin for "from something done afterward"

• Quasi- the prefix 'quasi' denotes methods that are "almost" or "socially approximate"

• Variable- a measurable factor, characteristic, or attribute of an individual or a system

ReferencesReferences

• Research Methods in Education 5th Edition, Louis Cohen, Lawrence, Manion and Keith Morrison 2004, New York

• http://en.wikipedia.org/wiki/Main_Page, 4/10/2007