Experimental Research In Health Care and Nursing

Health Care Experimental Research Design

What Is Experimental Research,Manipulation in Research,Research Control,Study Designs,Qualities of Research Study Designs.

What Is Experimental Research

    True experiments have the potential to provide strong evidence about the hypothesized causal relationship between independent and dependent variables. Experiments are characterized by manipulation, control, and randomization. The quality of experiments depends on the validity of their design.

Manipulation in Research

    Manipulation means the researcher actively initiates, implements, and terminates procedures. In most instances, manipulation is linked to the independent variable(s) under consideration. Essential to manipulation is that the researcher has complete control over the process. 

    The researcher decides what is to be manipulated (eg, selected nursing intervention protocols), to whom the manipulation applies (eg, samples and subsamples of subjects), when the manipulation is to occur according to the specification of the research design, and how the manipulation is to be implemented.

    Manipulation implies and is impossible without researcher control over extraneous sources that might affect and lead to incorrect scientific conclusions. Control aims "to rule out threats to valid inference." 

    It also adds precision, the "ability to detect true effects of smaller magnitude" (Cook, T., & Campbell, 1979, p. 8). Unlike laboratory studies where total control is often possible, in clinical research control is a relative matter. The researcher has the responsibility for ensuring as much control over extraneous forces as possible.

Research Control

    Control also includes "the ability to determine mine which units receive a particular treatment at a particular time" (Cook, T., & Campbell, 1979, p. 8). This refers to control over two processes that determine who gets what at what time. The first process is the researcher's use of random methods to assign subjects to treatments. 

    This is the preferred method of exerting control over subjects and their treatment as, theoretically, it ensures that known and unknown extraneous forces inherent to subjects are dispersed equally across the different treatment options. 

    This may not always be possible, in which case the second process comes into play-that of structuring the assignment process in such a way that major, known extraneous forces are controlled.

Study Designs 

    Commonly used design strategies include blocking, matching, and counterbalancing. In blocking the potentially confounding variable is incorporated into the study design as: an independent variable. Subjects are then randomly assigned within each block. 

    In matching, a weaker but very common method of control, the researcher identifies one or more extraneous (usually up to three) variables to be controlled. 

    As soon as a subject is recruited for one of the treatment groups, the researcher then tries to find subjects for the other group(s) identical to the first subject on the specified matching variables. Counterbalancing occurs when the researcher is concerned that the order in which treatments are administered influences the results. 

    When counterbalancing is used, all subjects receive all treatments; however, the order of administration of treatments is varied. Randomization entails two separate processes: 

(a) random selection of subjects from the population.

(b) random assignment of subjects to treatment and control conditions. 

    Random selection is the process of randomly drawing research subjects from the population about which the researcher wants to gain knowledge and to which the researcher hopes to generalize the findings of a study. 

    Random assignment entails allocating sampling units (eg, patients) to treatment and control conditions by using a decision method that is known to be random (eg, coin toss, random drawing, use of random tables, computer-generated random sequences of options). 

    Random selection is virtually nonexistent in intervention studies in nursing; moreover, a large proportion (55.3%) of nursing intervention studies do not even use random assignment methods (Abraham, Chalifoux, & Evers, 1992).

Qualities of Research Study Designs

    T Cook and Campbell (1979) reviewed four types of validity of research designs, potential threats to each, and strategies to remedy these threats. Statistical conclusion validity addresses the extent to which, at the mathematical/statistical level, covariation is present between the independent and dependent variables (ie, the extent to which a relationship exists between the independent and dependent variables). 

    Internal validity refers to whether an observed relationship between variables is indeed causal or, in the absence of a relationship, that indeed there is no causal link. 

    Construct validity of putative causes and effects refers to whether the causal relationship between two variables is indeed "the one" and tries to refute the possibility that a confounding variable may explain the presumed causal relationship.

    External validity refers to the generalizability of an observed causal relationship "across alternate measures of the cause and effect and across different types of persons, settings, and times" (Cook, T., & Campbell, 1979, p. 37). 

    Validity of any type is not a yes/no issue of whether or not it is present. Rather it is a matter of degree, determined by the extent to which the researcher has tried to cope with the various potential threats to each type of validity.