Critical Appraisal Process for Quantitative Research
As you critically appraise studies, follow the steps of the critical appraisal process presented in Box 18-1. These steps occur in sequence, vary in depth, and presume accomplishment of the preceding steps. However, an individual with critical appraisal experience frequently performs multiple steps of this process simultaneously. This section includes the three steps of the research critical appraisal process applied to quantitative studies and provides relevant questions for each step. These questions are not comprehensive but have been selected as a means for stimulating the logical reasoning and analysis necessary for conducting a study review. Persons experienced in the critical appraisal process formulate additional questions as part of their reasoning processes. We cover the identification of the steps or elements of the research process separately because persons who are new to critical appraisal often only conduct this step. The questions for determining the study strengths and weaknesses are covered together because this process occurs simultaneously in the mind of the person conducting the critical appraisal. Evaluation is covered separately because of the increased expertise needed to perform this final step.
Step I: Identifying the Steps of the Quantitative Research Process in Studies
Initial attempts to comprehend research articles are often frustrating because the terminology and stylized manner of the report are unfamiliar. Identification of the steps of the research process in a quantitative study is the first step in critical appraisal. It involves understanding the terms and concepts in the report; identifying study elements; and grasping the nature, significance, and meaning of the study elements. The following guidelines are presented to direct
you in the initial critical appraisal of a quantitative study.
Guidelines for Identifying the Steps of the Quantitative Research Process
The first step involves reviewing the study title and abstract and reading the study from beginning to end (review the key principles in Box 18-2). As you read, address the following questions about the research report: Was the writing style of the report clear and concise? Were the different parts of the research report plainly identified (APA, 2010)? Were relevant terms defined?
You might underline the terms you do not understand and determine their meaning from the glossary at the end of this textbook. Read the article a second time and highlight or underline each step of the quantitative research process. An overview of these steps is presented in Chapter 3. To write a critical appraisal identifying the study steps, you need to identify each step concisely and respond briefly to the following guidelines and questions:
A. Describe the qualifications of the authors to conduct the study, such as research expertise, clinical experience, and educational preparation. Doctoral education, such as a PhD, and postdoctorate training provide experiences in conducting research. Have the researchers conducted previous studies, especially studies in this area? Are the authors involved in clinical practice or certified in their area of clinical expertise (Fothergill & Lipp, 2014)?
B. Discuss the clarity of the article title (variables and population identified). Does the title indicate the general type of study conducted—descriptive, correlational, quasi-experimental, or experimental (Shadish et al., 2002)?
C. Discuss the quality of the abstract. An abstract should include the study purpose, design, sample, intervention (if applicable), and results; and highlight key findings (APA, 2010).
II. State the problem (see Chapter 5).
A. Significance of the problem
B. Background of the problem
C. Problem statement
III. State the purpose (see Chapter 5).
IV. Examine the literature review (see Chapter 7).
A. Were relevant previous studies and theories described?
B. Were the references current? (Number and percentage of sources in the last 10 years and in the last 5 years?)
C. Were the studies described, critically appraised, and synthesized (Fawcett & Garity, 2009; Hoe & Hoare, 2012)?
D. Was a summary provided of the current knowledge (what is known and not known) about the research problem (Wakefield, 2014)?
V. Examine the study framework or theoretical perspective (see Chapter 8).
A. Was the framework explicitly expressed, or must the reviewer extract the framework from implicit statements in the introduction or literature review?
B. Is the framework based on tentative, substantive, or scientific theory? Provide a rationale for your answer.
C. Did the framework identify, define, and describe the relationships among the concepts of interest? Provide examples of this.
D. Is a model (diagram) of the framework provided for clarity? If a model is not presented, develop one that represents the framework of the study and describe it.
E. Link the study variables to the relevant concepts in the model.
F. How was the framework related to the body of knowledge of nursing (Smith & Liehr, 2013)?
VI. List any research objectives, questions, or hypotheses (see Chapter 6).
VII. Identify and define (conceptually and operationally) the study variables or concepts that were identified in the objectives, questions, or hypotheses. If objectives, questions, or hypotheses were not stated, identify and define the variables in the study purpose and the results section of the study. If conceptual definitions were not included, identify possible definitions for each major study variable. Indicate which of the following types of variables were included in the study. A study usually includes independent and dependent variables or research variables but not all three types of variables.
A. Independent variables: Identify and define conceptually and operationally.
B. Dependent variables: Identify and define conceptually and operationally.
C. Research variables or concepts: Identify and define conceptually and operationally.
VIII. Identify demographic variables and other relevant terms.
IX. Identify the research design.
A. Identify the specific design of the study. Draw a model of the design by using the sample design
models presented in Chapters 10 and 11.
B. Did the study include a treatment or intervention (see Chapter 11)? If so, is the treatment clearly described with a protocol and consistently implemented, which indicates intervention fidelity (Forbes, 2009; Mittlbock, 2008; Morrison et al., 2009)?
C. If the study had more than one group, how were subjects assigned to groups (Kerlinger & Lee, 2000; Shadish et al., 2002)?
D. Were extraneous variables identified and controlled for by the design or methods? Extraneous variables usually are discussed in research reports of quasi-experimental and experimental studies (Shadish et al.,2002).
E. Were pilot study findings used to design this study? If yes, briefly discuss the pilot and the changes made in the study based on the pilot.
X. Describe the population, sample, and setting (see Chapter 15).
A. Identify inclusion or exclusion sample or eligibility criteria that designate the target population.
B. Identify the specific type of probability or nonprobability sampling method that was used to
obtain the sample. Did the researchers identify the sampling frame for the study (Kandola, Banner, Okeefe-McCarthy, & Jassal, 2014; Thompson, 2002)?
C. Identify the sample size. Discuss the refusal rate and include the rationale for refusal if presented in the article. Discuss the power analysis if this process was used to determine sample size (Aberson, 2010; Cohen, 1988).
D. Identify the sample attrition (number and percentage). Was a rationale provided for the study
E. Identify the characteristics of the sample.
F. Discuss the institutional review board approval. Describe the informed consent process used in the study (see Chapter 9).
G. Identify the study setting, and indicate whether it is appropriate for the study purpose.
XI. Identify and describe each measurement strategy used in the study (see Chapters 16 and 17). The following information should be provided for each measurement method included in a study. Identify each study variable that was measured and link it to a measurement method(s).
A. Identify the name and author of each measurement strategy.
B. Identify the type of each measurement strategy (e.g., Likert scale, visual analog scale, and physiological measure).
C. Identify the level of measurement (nominal, ordinal, interval, or ratio) achieved by each measurement method used in the study (Grove & Cipher, 2017).
D. Describe the reliability of each scale for previous studies, for this study, and for the pilot study if one was performed. Identify the precision of each physiological measure (Bartlett & Frost, 2008; Bialocerkowski, Klupp, & Bragge, 2010; DeVon et al., 2007; Polit & Yang, 2016).
E. Identify the validity of each scale and the accuracy of physiological measures (DeVon et al., 2007; Ryan-Wenger, 2010).
F. If data for the study were obtained from an existing database, did the researchers identify how, where, when, and by whom the original data were collected?
The following table includes the critical information about two measurement
methods, the Beck Likert scale to measure depression and the physiological
instrument to measure blood pressure. Completing this table allows you to
identify essential measurement content for a study (Waltz, Strickland, & Lenz,
XII. Describe the procedures for data collection and management (see Chapter 20).
XIII. Describe the statistical techniques performed to analyze study data (see Chapters 21, 22, 23, 24, and 25).
A. List the statistical procedures conducted to describe the sample.
B. Was the level of significance or alpha identified? If so, indicate what it was (0.05, 0.01, or 0.001).
C. Complete the following table with the analysis techniques conducted in the study: (1) identify the focus (description, relationships, or differences) for each analysis technique; (2) list the statistical analysis technique performed; (3) list the statistic; (4) provide the specific results; and (5) identify the probability (p) of the statistical significance achieved by the result (Gaskin & Happell, 2014; Grove & Cipher, 2017; Hayat, Higgins, Schwartz, & Staggs, 2015; Hoare & Hoe, 2013; Plichta & Kelvin, 2013).
XIV. Describe the researcher’s interpretation of the study findings (see Chapter 26).
A. Are the findings related back to the study framework? If so, do the findings support the study
B. Which findings are consistent with the expected findings?
D. Which findings were not expected?
E. Are the findings consistent with previous research findings (Fawcett & Garity, 2009; Tonelli, 2012)?
XV. What study limitations did the researcher identify?
XVI. How did the researcher generalize the findings?
XVII. What were the implications of the findings for nursing?
XVIII. What suggestions for further study were identified?
XIX. Was the researcher’s description of the study design and methods
sufficiently clear for replication?
Step II: Determining Study Strengths and Weaknesses
The next step in critically appraising a quantitative study requires determining the strengths and weaknesses of the study (see Box 18-1). To do this, you must have knowledge of what each step of the research process should be like from expert sources such as this textbook and other research sources (Aberson, 2010; Bartlett & Frost, 2008; Bialocerkowski et al., 2010; Borglin & Richards, 2010; Creswell, 2014; DeVon et al., 2007; Fawcett & Garity, 2009; Forbes, 2009;
Fothergill & Lipp, 2014; Gaskin & Happell, 2014; Grove & Cipher, 2017; Hoe & Hoare, 2012; Hoare & Hoe, 2013; Morrison et al., 2009; Polit & Yang, 2016; Ryan-Wenger, 2010; Shadish et al., 2002; Tonelli, 2012; Wakefield, 2014; Waltz et al., 2010; Whiffin & Hasselder, 2013). Another source for critical appraisal of research is the Critical Appraisal Skills Programme (CASP) that was developed in the United Kingdom with critical appraisal checklists provided online at http://www.casp-uk.net/#!casp-tools-checklists/c18f8 (CASP, 2013). The ideal ways to conduct the steps of the research process are compared with the actual study steps. During this comparison, you examine the extent to which the researcher followed the rules for an ideal study and identify the study elements that are strengths or weaknesses. Your critical appraisal comments need to be supported with documentation from research sources.
You also need to examine the logical links connecting one study element with another. For example, the problem needs to provide background and direction for the statement of the purpose. In addition, you need to examine the overall flow of logic in the study. The variables identified in the study purpose need to be consistent with the variables identified in the research objectives, questions, or hypotheses. The variables identified in the research objectives, questions, or hypotheses need to be conceptually defined in light of the study framework.
The conceptual definitions provide the basis for the development of operational definitions. The study design and analyses need to be appropriate for the investigation of the study purpose and for the specific objectives, questions, or hypotheses (Fawcett & Garity, 2009; Fothergill & Lipp, 2014). Many study weaknesses result from breaks in logical reasoning. For example, biases caused by sampling, measurement methods, and the selected design impair the logical flow from design to interpretation of findings (Borglin & Richards, 2010). The previous level of critical appraisal addressed concrete aspects of the study. During analysis, the process moves to examining abstract dimensions of the study, which requires greater familiarity with the logic behind the research process and increased skill in critical thinking (Whiffin & Hasselder, 2013).
You also need to gain a sense of how clearly the researcher grasped the study situation and expressed it. The clarity of the researchers’ explanation of study elements demonstrates their skill in using and expressing ideas that require abstract reasoning. With this examination of the study, you can determine which aspects of the study are strengths and which are weaknesses and provide rationale and documentation for your decisions.
Guidelines for Determining Study Strengths and Weaknesses. The following questions were developed to assist you in examining the different aspects of a study and determining whether they are strengths or weaknesses. The intent is not to answer each of these questions but to read the questions and make judgments about the elements or steps in the study. You need to provide a rationale for your decisions and document from relevant research sources such as those listed in the previous section and in the references at the end of this chapter. For example, you might decide the study purpose is a strength because it addresses the study problem, clarifies the focus
of the study, and is feasible to investigate (Fawcett & Garity, 2009; Fothergill & Lipp, 2014).
I. Research problem and purpose
A. Was the problem sufficiently delimited in scope so that it is researchable but not trivial?
B. Is the problem significant to nursing (Brown, 2014)?
C. Does the purpose narrow and clarify the focus of the study? Does the purpose clearly address the gap in the nursing knowledge?
D. Was this study feasible to conduct in terms of money commitment; the researchers’ expertise; availability of subjects, facilities, and equipment; and ethical considerations?
II. Review of literature
A. Was the literature review organized to show the progressive development of evidence from previous research?
B. Was a theoretical knowledge base developed for the problem and purpose?
C. Was a clear, concise summary presented of the current empirical and theoretical knowledge in the area of the study (CASP, 2013; Craig & Smyth, 2012; Fawcett & Garity, 2009; Wakefield, 2014)?
D. Did the literature review summary identify what was known and not known about the research problem, at the beginning of the study process, and provide direction for the formation of the research purpose?
III. Study framework
A. Is the framework presented with clarity? If a model or conceptual map of the framework is present, is it adequate for explaining the phenomenon of concern?
B. Is the framework linked to the research purpose? If not, would another framework fit more logically with the study?
C. Is the framework related to the body of knowledge in nursing and clinical practice at the time the study was conducted?
D. If a proposition or relationship from a theory is to be tested, is the proposition clearly identified and linked to the study hypotheses (Fawcett & Garity, 2009; Smith & Liehr, 2013)?
IV. Research objectives, questions, or hypotheses
A. Were the objectives, questions, or hypotheses expressed clearly?
B. Were the objectives, questions, or hypotheses logically linked to the research purpose (Fothergill & Lipp, 2014)?
C. Were hypotheses stated to direct the conduct of quasi-experimental and experimental research (Kerlinger & Lee, 2000; Shadish et al., 2002)?
D. Were the objectives, questions, or hypotheses logically linked to the concepts and relationships (propositions) in the framework (Fawcett & Garity, 2009; Smith & Liehr, 2013)?
A. Were the variables reflective of the concepts identified in the framework?
B. Were the variables clearly defined (conceptually and operationally) and based on previous research or theories (Fothergill & Lipp, 2014; Smith & Liehr, 2013)?
C. Is the conceptual definition of a variable consistent with the operational definition?
D. Did the operational definitions capture both the concept and the breadth of its manifestations in the population of interest?
A. Was the design used in the study the most appropriate design to obtain the needed data (Creswell, 2014; Hoe & Hoare, 2012; Shadish et al., 2002)?
B. Did the design provide a means to examine all of the objectives, questions, or hypotheses?
C. Was the treatment clearly described (Forbes, 2009)? Was the treatment appropriate for examining the study purpose and hypotheses? Did the study framework explain the links between the treatment (independent variable) and the proposed outcomes (dependent variables)?
D. Was a protocol developed to promote consistent implementation of the treatment to ensure intervention fidelity? Did the researcher monitor implementation of the treatment to ensure consistency? If the treatment was not consistently implemented, what might be the impact on the findings (Morrison et al., 2009)?
E. Did the researcher identify the threats to design validity (statistical conclusion validity, internal validity, construct validity, and external validity) and minimize them as much as possible? What threats to internal validity were actually controlled for in the design phase, and in what ways? (see Chapters 10 and 11; Shadish et al., 2002)?
F. Was the design logically linked to the sampling method and statistical analyses?
G. If more than one group is included in the study, do the groups appear equivalent?
H. If a treatment was implemented, were subjects randomly assigned to the treatment group, or were the treatment and comparison groups dependent? Were the treatment and comparison group assignments appropriate for the purpose of the study (Borglin & Richards, 2010)?
I. If a quasi-experimental design was implemented instead of an experimental one, was the decision justified by the researcher?
VII. Sample, population, and setting
A. Was the sampling method adequate for producing a sample that was representative of the target population (Kandola et al., 2014)?
B. If random sampling was employed, was the type of sample actually obtained representative of the accessible population?
C. What were the potential biases in the sampling method? Were any subjects excluded from the study because of age, socioeconomic status, or ethnicity without a sound rationale (Borglin & Richards, 2010; Thompson, 2002)?
D. Did the sample include an understudied or vulnerable population, such as young, elderly,
pregnant, or minority subjects?
E. Were the sampling criteria (inclusion and exclusion) appropriate for the type of study conducted?
F. Was the sample size sufficient to avoid a Type II error? Was a power analysis conducted to determine sample size? If a power analysis was conducted, were the results of the analysis clearly described and used to determine the final sample size? Was the attrition rate projected in determining the final sample size (Aberson, 2010; Cohen, 1988)?
G. Were the rights of human subjects protected?
H. Was the setting used in the study typical of actual clinical settings (Borglin & Richards, 2010)?
I. What was the refusal rate for the study? If it was greater than 20%, how might this have affected the representativeness of the sample? Did the researchers provide rationale for the refusals?
J. What was the attrition rate for the study? Did the researchers provide a rationale for the attrition of study participants? How did attrition influence the final sample and the study results and findings (Cohen, 1988; Fawcett & Garity, 2009)?
A. Did the measurement methods selected for the study adequately measure the study variables (Polit & Yang, 2016; Waltz et al., 2010)?
B. Were the measurement methods sufficiently sensitive for detection of small differences between subjects? Should additional measurement methods have been used to improve the quality of the study outcomes (Waltz et al., 2010)?
C. Did the measurement methods used in the study have adequate validity and reliability? What additional reliability or validity testing might have improved the quality of the measurement methods (Bartlett & Frost, 2008; Bialocerkowski et al., 2010; DeVon et al., 2007)?
D. Respond to the following questions, which are relevant to the measurement approaches used in the study:
1. Scales and questionnaires
(a) Were the instruments clearly described?
(b) Were techniques for completion and scoring of the
(c) Were validity and reliability of the instruments
described (DeVon et al., 2007)?
(d) Did the researcher reexamine the validity and
reliability of instruments for the present sample?
(e) If an instrument was developed for the study, was
the instrument development process described (Waltz
et al., 2010)?
(a) Were the entities that were to be observed clearly
identified and defined?
(b)Was interrater reliability described?
(c) Were the techniques for recording observations
described (Waltz et al., 2010)?
(a) Did the interview questions address concerns expressed in the research problem?
(b) Were the interview questions relevant for the research purpose and objectives, questions, or hypotheses?
(c) Did the design of the questions tend to bias subjects’ responses?
(c) Did the sequence of questions tend to bias subjects’ responses (Waltz et al., 2010)?
4. Physiological measures
(a) Were the physiological measures clearly described (Ryan-Wenger, 2010)? If appropriate, are the brand names, such as Hewlett-Packard, of instruments identified?
(b) Were the accuracy, precision, and error of physiological instruments discussed (Ryan-Wenger,
(c)Were the physiological measures appropriate for the research purpose and objectives, questions, or hypotheses?
(d) Were the methods for recording data from physiological measures clearly described? Was the
recording of data consistent?
IX. Data collection
A. Was the data collection process clearly described?
B. Were the forms used to collect data organized to facilitate computerizing the data? Did the subjects enter their data into a computer?
C. Was the training of data collectors clearly described and adequate?
D. Was the data collection process conducted in a consistent manner (Borglin & Richards, 2010)?
E. Were the data collection methods ethical?
F. Did the data collected address the research objectives, questions, or hypotheses?
G. Did any adverse events occur during data collection? If adverse events occurred, were these appropriately managed?
X. Data analysis
A. Were data analysis procedures appropriate for the type of data collected (Grove & Cipher, 2017; Hayat et al., 2015; Plichta & Kelvin, 2013)?
B. Were data analysis procedures clearly described? Did the researcher address any problems with missing data and how this problem was managed?
C. Did the data analysis techniques address the study purpose and the research objectives, questions, or hypotheses?
D. Were the results presented in an understandable way by narrative, tables, or figures, or a combination of methods (APA, 2010; Hoare & Hoe, 2013)?
E. Were the statistical analyses logically linked to the design?
F. Is the sample size sufficient to detect significant differences if they are present (Gaskin & Happell, 2014)?
G. Were the results interpreted appropriately?
XI. Interpretation of findings
A. Were findings discussed in relation to each objective, question, or hypothesis?
B. Were various explanations for significant and nonsignificant findings examined?
C. Were the findings clinically significant (Gatchel & Mayer, 2010; Tonelli, 2012)?
D. Were the findings linked to the study framework?
E. Were the study findings an accurate reflection of reality and valid for use in clinical practice?
F. Did the conclusions fit the results from the data analyses? Were the conclusions based on statistically significant and clinically important results?
G. Did the study have weaknesses not identified by the researcher?
H. Did the researcher generalize the findings appropriately?
I. Were the identified implications for practice appropriate, based on the study findings and the findings from previous research (Wintersgill & Wheeler, 2012)?
J. Were quality suggestions made for further research?
Step III: Evaluating a Study
Evaluation involves determining the credibility, trustworthiness, meaning, and usefulness of the study findings. This type of critical appraisal requires more advanced skills and might be performed by master’s and doctoral level students in determining current nursing knowledge and its usefulness in practice. Evaluating research involves summarizing the quality of the research process and findings, determining the consistency of the findings with those from previous studies, and determining the usefulness of the findings for practice. The steps of the study are evaluated in light of previous studies, such as an evaluation of present hypotheses based on previous hypotheses, present design based on previous designs, and present methods of measuring variables based on previous methods of measurement. Evaluation builds on conclusions reached during the first two stages of the critical appraisal so that the credibility, meaning, trustworthiness, and usefulness of the study findings can be determined for nursing knowledge, theory, and practice.
Guidelines for Evaluating a Study
You need to reexamine the discussion section of the study focusing on the study findings, conclusions, implications for practice, and suggestions for further study. It is important for you to read previous studies conducted in the area to determine the quality, credibility, and meaning of the study based on previous research. Using the following questions as a guide, summarize your evaluation of the study, and document your responses.
I. Did the study build upon previous research problems, purposes, designs, samples, and measurement methods? Provide examples to support your comments.
II. Could the weaknesses of the study have been corrected? How might that have been accomplished?
III. When the findings are examined in light of previous studies, do the findings build on previous findings?
IV. Do you believe the study findings are credible? How much confidence can be placed in the study findings (Tonelli, 2012)?
V. Based on this study and the findings from previous research, what is now known and not known about the phenomenon under study?
VI. To what populations can the findings be generalized (Cohen, 1988)?
VII. Were the implications of the findings for practice discussed? Based on previous research, are the findings ready for use in practice (Melnyk & Fineout-Overholt, 2015)?
VIII. Were relevant studies suggested for future research?
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