Page 390 - Encyclopedia of Nursing Research

OReM’S SeLF-CARe THeORy n 357

biased study threatens internal validity if the by masking the presence of an association
distortion is sufficient to lead to an errone- between the independent and the dependent
ous inference about the relationship between variables. A distinction between confound- O
the independent and dependent variable. ing bias and other types of bias is that con-
Potential sources of bias that can threaten the founding may be correctable at the design or
internal validity of observational studies are analysis stage of the study, whereas bias due
those related to selection, measurement, and to selection and measurement problems is
confounding. usually difficult or impossible to correct in the
Selection bias is a distortion in the esti- analysis. Confounding can be controlled or
mate of effect resulting from (a) flaws in the minimized at the design stage of the study by
choice of groups to be compared; (b) inability restricting the study sample or by matching
to locate or recruit participants selected into the comparison groups. At the analysis stage,
the sample, resulting in differential selec- confounding can be controlled or minimized
tion effects on the comparison groups; and by using a multivariable approach to the sta-
(c) subsequent attrition of participants who tistical analysis to adjust for the confounding
had initially agreed to participate, which factors or by examining the independent–
changes the composition of the comparison dependent variable relationship within spec-
groups. ified levels or categories of the confounding
Measurement bias occurs when the factors (stratified analysis). Confounding
independent variable or outcome (dependent variables should not be confused with media-
variable) is measured in a way that is system- tor and moderator variables.
atically inaccurate and results in distortion In summary, observational designs are
of the estimate of effect. The major sources prevalent in nursing research because they
of measurement bias are (a) a defective mea- are used to describe phenomena in early
suring instrument, (b) a procedure for ascer- stages of knowledge development and pro-
taining the outcome that is not sufficiently vide a basis for designing experimental
sensitive and specific, (c) the likelihood of interventions. In addition, they are the only
detecting the outcome dependent on the par- feasible approach to hypothesis testing when
ticipant’s status on the independent variable, it is unethical to manipulate the independent
(d) selective recall or reporting by study par- variable. In the absence of randomization
ticipants, and (e) lack of blind measurements and manipulation, myriad sources of bias
when indicated. can influence observations and conclusions
Because of the lack of randomization in drawn from naturally occurring events; thus,
a nonexperimental study, uncontrolled con- rigorous observational designs and methods
founding variables are a major threat to inter- are essential.
nal validity. Unless confounding factors are
controlled in the design of the study or in its Janet C. Meininger
analysis, distortion in the estimate of effect
will result. A confounding factor operates
through its association with both the inde-
pendent and the dependent variables. It can Orem’s self-care theOry
distort the results in either direction; that is,
it can lead to an overestimation of the rela-
tionship between the independent and the One of nursing’s grand theories, Orem’s Self-
dependent variables by producing an indi- Care Deficit Nursing Theory (SCDNT), is a
rect statistical association, or it can lead to an vital component of nursing’s philosophical
underestimate of the relationship between foundation. The impetus of the theory, to
the independent and the dependent variables define a curriculum for practical nursing, led