Research Designs and Methods
in Early Intervention
Research is a structured process for the purposes of establishing a body of knowledge,
determining effective practices, and improving the quality of services. Research findings
influence our decisions about effective interventions as part of the evidenced-based practice
process. It is important for early intervention service providers to understand the basic
composition of research to interpret the literature for application to practice.
Research Terminology
There are terms that the early intervention provider should be familiar with when reading
research reports. Below are some of the more common terms and concepts found in research.
This list is not comprehensive list; for further explanation of terms used in research see the
References and Resources section end of this document.
Term
Bias
Control group
Population
Sample
Definition
The errors that can occur within a research study because of
the design or things not under the control of the researchers
Examples of bias include the control and the intervention
group not well matched in age, gender or condition
(selection bias), the measurement tool is not sensitive to
change (measurement bias), or the control group receives the
same or similar intervention as the study group (intervention
bias).
The group that does not receive the intervention so that a
comparison can be made. The control group is usually
matched in terms of age, gender, condition, etc.
All the possible individuals that the research applies to.
A group of participants in the study taken from a population.
The sample should represent the population that the research
will be applied to. The sample should be of sufficient size
for the results to be generalized to the larger population and
is statistically calculated before the sample is recruited to
participate.
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Variables
Validity
Reliability
The entities in research that fluctuate or change. This can be
anything from age and gender to the communication skills in
a toddler.
Independent variable- the variable that is manipulated in the
research like the treatment or intervention.
Dependent – the variable that is affected by the intervention.
The extent to which the study actually measures or reflects
what the research intended.
Internal validity- extent to which the design and methods are
appropriate for the purpose of the study.
External validity- the applicability or generalizability of the
research results.
The extent to which the research measures or procedures can
be repeated.
Ethics
Before conducting the studies, researchers are required to ensure the safety of participants and
conduct studies limiting bias and influence. The research article should explain the methods
used to protect the rights and welfare of the participants. Usually, a reference is made to
obtaining the approval of the project through an Institutional Review Board (IRB) from the
university the researcher or group is associated with.
The IRB is responsible for approval, monitoring, and reviewing biomedical and behavioral
research associated with the university. Article publication in professional journals also requires
the researcher to disclose conflicts-of-interest or financial interests which may potentially bias or
influence the research such as employment, consultancies, stock ownership, paid testimony,
funding sources, etc.
Approach
Before understanding the designs and methods, it is important to understand the framework or
approach a researcher uses. There are two main approaches to research in early intervention:
quantitative and qualitative. The quantitative research approach is the most common and
traditional. It focuses on the measurement of variables that are manipulated to determine if an
effect is produced. For example, a new intervention to improve articulation is compared to
traditional intervention by measuring and comparing the scores on a standardized articulation
assessment tool among two groups of children.
The qualitative research approach is used to understand the natural experiences, patterns, or
perceptions of individuals or groups. For example, a qualitative approach would be used to
understand the perception of the children and their families who received the new articulation
intervention. Some researchers utilizes both approaches together to more fully understand both
the effect and the perception of an intervention and these are called mixed methods studies.
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Design
The design of the research is either experimental or non-experimental. Experimental designs are
used to investigate the causal relationship or effect of an intervention or treatment. The research
involves controlling the variables (intervention, treatment, duration, etc) of an activity using
groups receiving and not receiving the intervention or a time series with and without the
intervention to make comparisons.
Non-experimental designs look at naturally occurring behaviors and contexts in groups or
individuals without controlling variables to observe and describe behavior or events or
understand relationships.
Experimental and Non-Experimental Research Methods
Design
Method
Experimental design
Randomized
Controlled
Trial
Time Series
Repeated
Measures
Cohort
Study
Single
system
studies
Description
Purpose
Randomly assignment or
groups of participants or
individuals into an
intervention or nonintervention condition
Baseline measurements or a
group or individuals are
compared to measurements
during and after treatment is
introduced for comparison
Same individuals are
measured at specific points in
time. Similar to time series
but the intervention and
comparison happens within
the individual
Non-random assignment or
naturally occurring groups
that are followed over time.
One group is exposed to the
intervention, the other was
not.
Focused on one individual or
small group in a specific
setting, data is taken over a
period of time is prior to,
during, and sometimes after
an intervention is completed
or withdrawn
To determine if the
manipulation of variables
causes a change between
groups or determine
effectiveness of an intervention
Useful to look at the effect of
an intervention when a
comparison group is not
ethical or practical
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Useful for controlling for age
and gender or comparing the
effect of different interventions
within the same individual.
Useful to look at the effect of
an intervention for when
random assignment is not
ethical or practical
To determine the effect of an
intervention in specific
situation on an individual or
small group
Non-experimental
Single
subject
Case Study
Surveys
Case report
Qualitative
approach
methods
Measurements are taken of an
individual during a baseline
period followed by an
intervention period. Can also
include measurement in a
period after cessation of the
intervention
Detailed, in-depth and
longitudinal investigation of
an individual, small group or
event where data is collected
and analyzed
Survey of a population or
large group at a point in time
or over time if repeated
Description of an intervention
used with an individual
Several methods
(ethnography,
phenomenonology, grounded
theory) are used to get very
detailed information about
relationships, experiences or
perceptions about
interventions or service
systems
Observation of the effect of
intervention within one
individual
To detail the specific nature of
an individual or small group
during an intervention or
event.
To measure and understand the
attitudes, experiences, opinions
or behaviors in a population
To test theories that may
impact practice or suggest
areas of future research
To describe the culture around
an issue or group
(ethnography), understand the
views of individuals or groups
(phenomenology), or develop
theories or understand
relationships (grounded
theory)
Methods
There are many methods used to investigate research questions in the experimental and nonexperimental designs. Experimental methods attempt to control the variables in the experiment
to the greatest extent possible so that any differences between groups or within an individual can
be attributed to the variables manipulated or intervention given. Examples include randomized
control trials, cohort studies, time series, repeated measures, and single subject methods. In
some research disciplines, research methods that do not strictly randomly assign groups, as with
cohort studies or single subject methods are called quasi-experimental.
Randomized control trials are considered to be the most rigorous type of experimental research
because the experiment has controlled the variables so that any results are most likely due to the
treatment or intervention rather than chance and bias. However, research with random
assignment or with controlled variables may not be practical, ethical or answer all questions
pertaining to interventions or service systems in early intervention. Non-experimental methods
were developed to observe, describe, or understand natural patterns, perceptions, and
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relationships surrounding or within interventions or service systems. Case reports, surveys,
research for generating norms on assessment tools, and qualitative research methods like
ethnography are examples of non-experimental designs.
Analysis
For quantitative research, statistical analysis is used to describe, compare groups, and determine
relationships or patterns. Below are some common statistical analysis used in research related to
early intervention.
Common Statistical Terms in Quantitative Research
Term
Description
Analysis of variance
Test for significant differences between means of groups.
This statistical tool allows comparison of multiple groups
or of multiple variables.
Correlation
The relationship between two or more variables usually
measured on a scale from -1.00 (a negative correlation) to
1.00 (a positive correlation) with zero meaning no
correlation between the variables.
Descriptive statistics
Statistics that describe a variable in the study
Mean- central tendency of variable
Confidence interval – the range of values around the mean
Distribution-frequency of the values around the mean
Odds Ratio
The comparison of the probability that a certain event is
the same for two groups. Measure of the benefit or risk of
an intervention in terms of the odds that the experimental
group experiences an event relative to the control group.
p-values and statistical
The calculation of probability that a relationship or
significance
difference between variables occurred by chance. P stands
for probability. If the p-value is numerically very low (.01,
.005, .001 ), then the relationship or difference is called
statically significant and not likely due to chance.
Power and sample size
Experiments have to be designed to ensure they are
detecting actual change. Power analysis allows the
researcher to calculate how large of a sample will be
needed for the experiment to reliably detect change due to
an intervention and the likelihood that the statistical tests
used will detect effects with a certain number of
participants.
t-scores, z-scores
The calculation the distribution of raw scores to standard
scores or values around the mean when the value of the
mean and standard deviation are known (z-score) or not
known and have to be estimated (t-score). Comparisons of
values can be made within the normal distribution around
the mean.
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Regression analysis
Measurement of the link or relationship between two or
more variables. Calculations of an estimation of the effect
one variable may have on another or others are used and as
well as a calculation of the probability of how close the
estimation may be to the real relationship.
Basic Statistics http://www.statsoft.com/textbook/basic-statistics/?button=1
Stat Trek http://stattrek.com/
MIT News Explained: Regression Analysis http://web.mit.edu/newsoffice/2010/explained-reganalysis-0316.html
For qualitative research, the analysis consists of determining patterns in detailed descriptions of
content in interviews or documents. Common analysis used within this approach is below.
Analysis in Qualitative Research
Term
Description
Grounded theory and
Comparison of one piece of data (interview, statement,
constant comparative
theme) with other data to discover themes or patterns.
analysis
These patterns are then given names or codes and are used
to compare with more data and are revised as new themes
or patterns emerge. When no more themes emerge and no
new data is helpful in discovering new patterns or themes,
the researcher reaches theoretical saturation. The pattern
or themes are then analyzed for concepts and categories
that can explain the experiences of people in the
circumstance of interest.
Ethnographic
Emersion in the culture of a group to analyze information
about how individuals or social groups understand or
experience events and phenomena within and through their
culture including beliefs, relationships, and lifestyles.
Phenomenological
Collecting and reflecting on data (interviews, documents)
in great detail not look for patterns or similarities, but to
understand the essence, nature, or what the meaning of and
experience is to a person or group.
Narrative analysis
Examination of an individual or group of individuals that
analyzes as the data the way they tell their story, the
language used, the interaction of interviewer and story
teller, and/or the use of words and gestures to understand
the life stories of individuals or organizations.
Ratcliff, D. Qualitative Research Resources http://qualitativeresearch.ratcliffs.net/resources.htm
Thorne, S. (2000). Data analysis in qualitative research Evidence Based Nursing. 3, 68-70
http://ebn.bmj.com/content/3/3/68.full
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Levels of Research Evidence
Each research approach, design, and method is used answer specific research questions. It is
important to know that although the experimental design and methods may yield a better
understanding of causation, the non-experimental designs are useful in understanding
relationships, provider and family experiences, and perceptions of interventions. This dispels the
common misperception that non-experimental research is not as valuable in understanding
intervention and other phenomena.
All of the information from the various types of research has value for making decisions about
using different interventions with individual children and families. It is important, however, to
have a process to categorize research evidence in terms of the strength of evidence for making
decisions in early intervention practice. The chart below is a commonly used quick guide to
determine the strength of evidence presented in research publications (adapted from Greenhalgh,
1997; Law 2002).
Levels of Evidence Grid
Rigor
Type of Research
1 High Systematic review and metaanalyses
2
Randomized Control Trials
3
Cohort studies (also called
prospective studies)
4
Single subject studies
5
Case studies
6
Cross-sectional surveys
7
Case report
Low
Definition
The results of several studies are
analyzed in standardized or statistical
process and conclusions from the total are
drawn
Randomly assignment or groups of
participants or individuals into an
intervention or non-intervention
condition
Non-random assignment or naturally
occurring groups that are followed over
time. One group is exposed to the
intervention, the other was not
Measurements are taken of an individual
during a baseline period followed by an
intervention period. Can also include
measurement in a period after cessation
of the intervention
Detailed, in-depth and longitudinal
investigation of an individual, small
group or event where data is collected
and analyzed
Survey of a population or large group at
one point in time
Description of an intervention used with
an individual
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References and Resources
Bryman, A. (2004). Social Research Methods (2nd ed.). New York: Oxford University Press, Inc.
Domholdt, E. (2000) Physical Therapy Research: Principles and Application. Philadelphia:
W.B.Saunders Company.
Greenhalgh, T.(1997). How to read a paper series in BMJ available from Pub Med Central in the
National Center for Biotechnology, National Library of Medicine at the National Institutes of
Health
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pmc&Term=greenhalgh+t%5BAuthor%5D+AND
+1997%5BPublication+Date%5D
Law, M & MacDermid, J. (Eds.). (2008). Evidence-Based Rehabilitation: A Guide to Practice (
2nd ed). Thorofare, New Jersey: SLACK, Inc..
Levels of Evidence Resources
American Academy for Cerebral Palsy and Developmental Medicine (AACPDM) (2008) has
Developed a methodology for creating systematic reviews including levels of evidence contained
in the appendix.
http://www.aacpdm.org/membership/members/committees/treatment_outcomes_methodology.pdf
Bogucka, R & Wood, E. (2009) How to read scientific research articles: A hands-on classroom
exercise. Issues in Science and Technology Librarianship, 59 http://www.istl.org/09fall/article4.html#9
Centre for Evidence-Based Medicine (CEBM) Levels of Evidence
Document that systematizes searching for evidence for different types of questions and
determining the levels of evidence http://www.cebm.net/index.aspx?o=5653 and
http://www.cebm.net/mod_product/design/files/CEBM-Levels-of-Evidence-2.pdf
Educational Practices Supported by Rigorous Evidence: A User Friendly Guide
http://www2.ed.gov/rschstat/research/pubs/rigorousevid/rigorousevid.pdf
How to read a scientific paper. West Lafayette (IN): Purdue University Libraries.
http://www.lib.purdue.edu/phys/assets/SciPaperTutorial.swf
Puruggannan, M. & Hewitt, J. 2004. How to Read a Scientific Article. Houston (TX): Rice
University. Cain Project for Engineering and Professional Communication.
http://www.owlnet.rice.edu/~cainproj/courses/HowToReadSciArticle.pdf
Research Designs and Methods
MC3 Mid Continent Comprehensive Center: Types of Research Designs
http://www.mc3edsupport.org/community/knowledgebases/types-of-research-design-800.html
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Research Methods Knowledge Base (2006)
http://www.socialresearchmethods.net/kb/desintro.php
Types of Research Methods, The SERVE Center, University of North Carolina at Greensboro
(2008)
http://www.doe.k12.ga.us/DMGetDocument.aspx/Types.of.Research.Methods.SERVE_Center.p
df?p=6CC6799F8C1371F6D55BAEF6711580176FB90D7CDA837A6C3F76C195C0821D6C&
Type=D
Research Terms
Writing @ CSU (Colorado State University)
http://writing.colostate.edu/guides/research/glossary/
Cite As: Georgetown University Center for Child and Human Development. Research Designs
and Methods in Early Intervention. 2011. Available online at http://www.teachingei.org.
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