I want to test a wound treatment or educational program but I have no funding or resources,
How do I do it?
Implementing & evaluating wound research conducted using pre-experimental designs part II
AAWC WocSpec Research Committee, Barbara M. Bates-Jensen, PhD, RN
ABSTRACT
PURPOSE: To provide information on how to evaluate and improve
methodology of wound research conducted using pre-experimental designs.
BACKGROUND: Research methodology is concerned with how a study’s
design is implemented and how the research is conducted. Methodology
determines the quality of the data generated by the study and specifies: when
and how often data are collected, construction of data collection measures, who
data is collected from, how data is analyzed, and how findings are presented.
Study design is a part of research methodology but not the only part.
METHODS: Pre-experimental studies include: case study design, static group
comparison or cross sectional design, and one group pre-test/post-test design
including longitudinal time series and panel designs. These designs are
frequently concerned with answering questions using an experimental approach
when resources are not available for conducting more rigorous experimental
designs. We often use pre-experimental designs for description and thus we are
concerned with how to answer questions such as: How many? How much?
How efficient? How effective? How adequate? We present information on
conducting static group comparisons and one group pre-test/post-test designs
for wound research. Advantages and disadvantages and methods for
increasing the strength of pre-experimental wound studies are outlined.
CONCLUSIONS: Pre-experimental designs follow basic experimental steps but
do not include a control group. Usually a single group is studied but no
comparison between an equivalent control group is made. The aim of preexperimental design is to evaluate the influence of a variable or to determine
the influence of a variable on one group and not on another. Limitations of one
group pre-test/post-test designs are that the approach provides a measure of
change but cannot provide conclusive results. Weakness in static group
comparison designs lies in the failure to examine equivalence of groups before
the implementation of the wound treatment or educational program. Methods to
improve the quality of wound research using pre-experimental designs include
attending to: historical events that may have occurred between the pre-test and
post-test, maturation changes in the subjects, difficulties with pencil and paper
measures for pre-tests and post-tests, instrument changes/calibration,
subject/wound selection biases.
BACKGROUND
Research methodology determines the quality of
the data collected in a study, it concerns how the
design is implemented and specifies:
• when and how often data are collected
• development of data collection measures &
instruments
• who data is collected from (the sample)
• how data are analyzed
• how findings are presented.
Whether or not study results are really the result of
the variable on the group under investigation in the
study (internal validity) and not some other variable
AND
Whether or not the study results can be expected
to be the same with other groups of people
(external validity) are issues that are addressed by
methodology.
Research design is an important part of
methodology. Study design is a part of research
methodology but not the only part.
In general, a research design is the plan for the
research study. The design guides when and how
often to collect data, what data to gather and from
whom, and how to analyze the data.
A research design refers to the type of study that
will be conducted, whether it will be preexperimental, quasi-experimental, or true
experimental.
PRE-EXPERIMENTAL METHODS
Pre-experimental research designs:
 answer questions using an experimental
approach when resources are not available for
conducting more rigorous experimental designs
are used to describe a variable
often answer questions such as: How many?
How much? How efficient? How effective? How
adequate?
follow basic experimental steps but do not include
a control group
usually involve study of a single group with no
comparison between an equivalent control group
The aim of pre-experimental design is to evaluate
the influence of a variable or to determine the
influence of a variable on one group and not on
another.
There are 3 pre-experimental research designs:
1. case study
2. static group comparison/cross sectional
3. one group pre-test/post-test (longitudinal
time series and panel)
One group pre-test/post-test
designs
Treatment Group
O1
X
O2
X = Wound Treatment or Educational Program
O1 = Pre treatment or educational program observation
measurement or Pretest
O2 = Post observation measurement or Posttest
 1 group gets the wound treatment or education.
A
pretest or pre-observation measure is taken first to
establish baseline knowledge or initial wound
outcomes, then a posttest or post observation measure
is determined to measure the difference between the
pretest and posttest. There is no comparison group.
What happens in a One group pretest/post-test design:
 Data is collected on relevant variables before and
after the wound treatment or education from subjects.
The same data is collected for the pretest and
posttest.
Data is collected repeatedly over a long period of
time.
If data are collected on the same variable at regular
intervals it is a time series design; reveals changes in
the aggregate such as in a population.
If data are collected from the same subjects over
time it is a panel design; reveals changes at individual
level.
Findings reveal different patterns or trends.
advantages
TIME SERIES
Data are easy to collect
Results are easy to present in graphs
Interpretation is relatively easy
PANEL
Reveal changes at the individual level
Establishes time order of variables
Can explain how relationships emerge.
limitations
Takes longer to complete the study because of
the longitudinal nature of the design
TIME SERIES
Data collection method may change over time
Difficult to show more than one variable at a time
May need qualitative research to explain
fluctuations
Assumes present trends will continue
unchanged.
PANEL
Difficult to obtain initial sample of subjects
Difficult to keep the same subjects over time
Repeated measures may influence
subjects’behavior.
How to make One group pre-test/posttest designs stronger:
Treatment
Group
Comparison
Group
O1
O2
O3
O1
O2
O3
X
O4
O5
O4
O5
X = Wound Treatment or Educational Program
O1 O2 O3 = Pre treatment or educational program observation
measurements or Pretests
O4 O5 O6 = Post observation measurements or Posttests
Add a comparison group.
The O1 O2 O3 pretests allows determination of
any differences between the treatment and
comparison group before the wound treatment
or educational program is delivered so any
difference in the posttests or post observation
measurements are more likely to be related to
the wound treatment or educational program.
The comparison group allows evaluation of
the effects of:
 history (something happening during the
data collection time points)
maturation (something happening to the
subjects during the data collection time
points)
Some considerations to improve
One group pre-test/post-test
studies
Use the same pretest and posttest measures.
Gather the same number of pretest measures as you
do posttest measures
Conduct reliability testing throughout the duration of the
study to control for measurement drift and to be sure the
same measurement process is used for all pretests and
posttests
Be sure any equipment is routinely calibrated during
long studies
Report drop-out rates and run analyses using an
intention to treat approach (include those that drop out)