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Extraneous Variables and plan for Control

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Extraneous variables are factors that have the potential to influence the outcome of an experiment, though they are not the center of focus. There is a need for controlling the undesirable influence as the elements can lower the internal validity of a study. While the study acknowledges that air mattresses are effective in offsetting the risk of decubitus ulcers through the hydrostatic distribution of pressure and provision of a comfortable surface that is critical in pain management and airflow, it also recognizes that other situational aspects can have the same outcome. One such aspect is placement, a prevention strategy that exploits the power of switching positions in preventing the buildup of pressure. Similarly, risk assessment helps in detecting minor incidences, a move that is helpful in preventing progression of wounds to grade 3 and 4 (Pancorbo‐Hidalgo, Garcia‐Fernandez, Lopez‐Medina, & Alvarez‐Nieto, 2006). Skin management approaches such as the use of protectants and moisturizing cream also have similar outcomes as the use of air mattresses, a clinical benefit that is also observed in the use of pillows in preventing bedsores in high-risk regions such as sacral region, heels, elbows, and shoulders (Bluestein & Javaheri, 2008). To control the influence of the situational differences across long-term care facilities, the study will standardize procedures, where positioning, pillows, and skin cleaning will be part of the prevention bundle (Austin, 2011). The only different exposure will be the type of mattress being used, a move that will help capture the attributive effects.

Another source of contingent effects on the relationship between the independent variable and the dependent variable is the selection of participants.  The influence of the participant effect is a confirmed issue, with the current body of evidence highlighting that cases that are confined to wheelchairs and bedridden report elevated risk. Picking such groups would result in a number of biases. The undesirable effects will be controlled through homogenization of the sample, where persons above 60 years and those with more than three chronic conditions will be purposely screened out. The control will not only reduce the influence of extraneous variables, but will also promote the robustness of the study by increasing external validity, where participation will only consider people aged 50-60 years. Similarly, the nested case-control sampling approach will ensure both randomization and homogeneity, where every case participating will be matched by 4 in the control group.

Instruments: Description, Validity, and Reliability


The two primary tools of data collection will be an observation checklist as well as an interviewer-administered semi-structured questionnaire. The choice has been influenced by the power of the tools in gathering data on both study and demographic variables. Both the checklist and the questionnaire are relatively easy to use, thus addressing financial and time constraints that characterize the data collection process (Bourdon, Goodman, Rae, Simpson & Koretz, 2005). Nevertheless, both the questionnaire and the checklist cannot be used in documenting emotions and feelings, a shortfall that will be addressed by visual analog scale (VAS). The psychometric scale captures nominal aspects such as attitudes among other subjective responses that cannot be quantified. Similarly, the tool is also valuable in ordinal scale because of its effectiveness in capturing the level of comfort of using air mattresses along a continuous line as the case of Likert-type responses.

Validity and Reliability Estimates

While reliability focuses on the extent to which a tool produces consistent results, validity explores the degree to which a concept is well-founded.  The two concepts will find enormous relevance in determining the suitability of the instrument in this study, with the reliability estimates providing data for improving accurateness of the device. With the tool being adopted from the current stock of literature, internal consistency and content validity will be promoted by considering the views of scholars who may have employed the device as well as critical reviews surrounding the use of the apparatus.

One of the aspects of testing validity will be the adoption of the operationalization of the research objectives. The plan will be complemented by approaches embraced to control the undesirable influence of extraneous variables. The external validity, which focuses on determining the extent to which the findings of a study can be generalized to the population of interest, will be achieved through randomness in sampling process as well as ensuring homogeneity in the sample. Similarly, Crohn Bach’s alpha test will be used to enhance the reliability of the data collection instruments (Sijtsma, 2009). The reliability and validity of the instruments will also be ascertained by a pilot study, where the primary objective will be establishing the appropriateness and the consistency of the tool. Appropriate changes will be made based on the findings.

Description of the Intervention

The intervention focus is establishing the attributive benefits of air mattresses in preventing incidences of bedsores in long-term care facilities. The intervention will be guided by a nested case-control design, where new cases will be documented prospectively among the subset of residents using standard and air mattresses. The trends in the incidences of bedsores in the cohort will be compared for four months.

Data Collection Procedures

The focus of the interventional study is to continuously document new cases of bedsores using a checklist in a long-term care facility for four months. Similarly, structured questionnaires will be employed among managers of the facilities to offer expert opinion on the use of standard mattress and air mattresses and their role in offsetting the risk of pressure ulcers.

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