ABSTRACT

1. I want to test a wound treatment or educational program in my clinical setting with patient groups that are convenient or that already exist, How do I do it? Implementing & evaluating wound research conducted using quasi-experimental designs AAWC WocSpec Research Committee, Barbara M. Bates-Jensen, PhD, RN • Statistical Regression:occurs when groups have been selected based on extreme scores. • Use a control group and randomization . Select groups that are not at the extreme of characteristics. • Selection: biases resulting from the differential selection of subjects. • Use of randomization procedures and pretesting can help by determining the presence or knowledge that exist before the treatment. • Experimental Mortality:the differential loss of subjects from the comparison groups. • Use pretesting as subjects can be removed from the entire comparison by removing their pretest. • Selection-Maturation Interaction:interaction effects between the selection and maturation which can be mistaken for the effects of the experimental variable. • Use a control group and randomization QUASI-EXPERIMENTAL METHODS ABSTRACT Nonequivalent Before-after Designs PURPOSE: To provide information on how to evaluate and improve methodology of wound research conducted using quasi-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: Quasi-experimental studies include: pretest posttest nonequivalent group design, time series design, and non-equivalent before-after design. The purpose of quasi-experimental research is to approximate the conditions of the true experiment in a setting which does not allow the control and/or manipulation of all relevant variables. The researcher must clearly understand what compromises exist in the internal and external validity of the design and proceed within these limitations. We use quasi-experimental designs in the clinical setting when control of all variables is not possible. Quasi-experimental designs are better than pre-experimental studies in that they use a method of comparing groups. They are limited in that they fail to randomize the groups. This research is characterized by methods of partial control based on a careful identification of factors influencing both internal and external validity. Methods of increasing the strength of quasi-experimental wound studies are outlined. CONCLUSIONS: Quasi-experimental designs follow true experimental steps but typically do not control all variables and do not include randomization. The aim of quasi-experimental design is to evaluate the influence of a variable on one group and not on another. Limitations relate to the researcher’s attention to internal and external validity. Methods to improve the quality of wound research using quasi-experimental designs include attending to internal validity or did the treatment make the difference in this specific instance rather than other factors? And external validity or to what populations, settings, or treatment variables can this observed effect be generalized? • The purpose of quasi-experimental research is to approximate the conditions of the true experiment in a setting which does not allow the control and/or manipulation of all relevant variables. Quasi-experimental research designs: • answer questions using as much of an experimental approach as possible in a clinical setting • follow basic experimental steps but do not include randomization and may not control other variables; uses existing or convenient groups • Quasi-experimental research designs include: • Pretest posttest nonequivalent group design • Time series design • Non-equivalent before-after design O1 = Pre observation measurement or Pretest X = Wound Treatment or Educational Program O2 = Post observation measurement or Posttest • Two groups with known differences before the study begins are tested and compared. • The same treatment is done for both groups and differences in posttests are assumed to be related to the difference in the two groups. Improving Quasi-experimental studies: Internal Validity Quasi-experimental studies: External Validity • Internal Validity asks the question: did, in fact, the experimental treatments make a difference in this specific instance? • 8 classes of extraneous variables which, if not controlled, may produce effects that can be confused with the effects of the experimental treatment: • History: Did something happen between the first and second measurements in addition to the treatment which might affect the measurement? • Use a control group. • Maturation: the process of growing, developing, aging or maturing which takes place in the individual during the study period. • Use a control group. • Pre-testing: the effect created on the second measurement by having a measurement before the experiment (the pre-test). • Use additional groups that do not receive the pretest or experimental treatment. These groups are in addition to the regular control group. • Instrumentation: changes in measurement due to changes in instrumentation calibration or changes in the observers. • Use a control group. Use quality control monitoring during the study to help detect/control changes in instrument use/measurement. Include reliability testing throughout the study, include instrument calibration and adequate training. Pretest Posttest Nonequivalent Group Designs • External Validity asks the question: to what populations, settings, treatment, and measurement variables can this effect be generalized? • Just like internal validity, 4 classes of variables which, if not controlled, may produce effects that can only be attributed to the specific sample, setting, and procedures in the current study. Thus, there is no way to use the findings with other groups. • Interactioneffects of Selection and the experimental variable. Subjects selected from a small group or one with particular characteristics can’t be generalized to any larger group. • Reactive or Interactioneffect of Pretesting- the pretesting modifies the subjects in such a way that they respond to the experimental treatment differently than will un-pretested persons making them unrepresentative of the population. • Reactive effects of experimental procedures arising from the experimental setting which will not occur in non-experimental settings. • Multiple-Treatment Interference effects due to multiple treatments applied to the same subjects so the findings can only be generalized to persons exposed to the same treatments in the same order of presentation. 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. O1 = Pre observation measurement or Pretest X = Wound Treatment or Educational Program O2 = Post observation measurement or Posttest • A strong and widely used quasi-experimental design. • Differs from true experiments because there is no randomization, the groups are not equal. • Comparing pretest results can show the level of equivalence between the groups. Time Series Designs O1 –O3= Pre observation measurements or Pretests X = Wound Treatment or Educational Program O4 –O6 = Post observation measurement s or Posttests • To determine the influence of a variable introduced after a series of initial observations • Differs from true experiments because there is no randomization, the groups are not equal. • Comparing pretest results can show the level of equivalence between the groups.