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Chapter 20

Clinical Significance and Interpretation of Quantitative Results

Question

Tell whether the following statement is true or false:

Results of a study need to be evaluated with thought to the aims of the study.

Answer

True

The results need to be evaluated and interpreted, giving thought to the aims of the study, its theoretical basis, the body of related research evidence, and limitations of the adopted research methods.

Question

Tell whether the following statement is true or false:

Methodologic decisions affect the inferences that can be made between study results and the real clinical world.

Answer

True

Inference is central to interpretation. Methodologic decisions made by researchers affect the inferences that can be made about the correspondence between study results and “truth in the real world.”

Interpretation of Quantitative Research Results

The credibility of the results

Precision of estimates of effects

Magnitude of effects

Underlying meaning of the results

Generalizability of results

Implications for future research, theory development, and nursing practice

Credibility of Quantitative Results

Proxies
Validity
Bias
Corroboration
Precision and meaning of results
Magnitude of effects and importance
Interpreting hypothesized results

Interpretation of Quantitative Research Results (cont.)

Inference is central to interpretation.
Methodology affects inferences about the correspondence between results and the “real world.”
A cautious outlook is appropriate.

Question

Tell whether the following statement is true or false:

Credibility assessments involve a careful assessment of validity threats and biases that could undermine the accuracy of the results.

Answer

True

Credibility assessments can involve a careful assessment of study rigor through an analysis of validity threats and biases that could undermine the accuracy of the results.

Credibility Assessment

Approaches include:
Evaluating the degree of congruence between abstract constructs and the proxies actually
Careful assessment of study rigor
Corroboration (replication) of results

Clinical Significance

Group-level results is often inferred on the basis of such statistics as effect size indexes, confidence intervals, and number-needed-to-treat.
Individual results is discussed in terms of effects.

Clinical Significance (cont.)

Benchmark: threshold that designates a meaningful amount of change
Ask whether:
A change in the attribute is real
A patient in a dysfunctional state returns to normal functioning
A patient has achieved a symptom state that is acceptable to them
The amount of change in an attribute can be considered minimally important

Clinical Significance (cont.)

Minimal important change (MIC)
Value for the amount of change score points that an individual patient must achieve in order to be credited with having a clinically important change

Clinical Significance (cont.)

Methods of establishing the MIC:

A consensus panel
An anchor-based approach
A distribution-based method
Bases the MIC on the distributional characteristics of the sample
Triangulation of approaches is increasingly common.

Clinical Significance (cont.)

MICs cannot be used to interpret:

Group means
Differences in means
MICs can be used to interpret:
If each person in a sample has or has not achieved a change greater than the MIC
Responder analysis compares the percentage of responders in different study groups.

Group Level

Group-level clinical significance (practical significance)

Involves using statistical information other than p values to draw conclusions about the usefulness or importance of research findings
Most widely used statistics
Effect size (ES) indexes
Confidence intervals (CIs)
Number-needed-to-treat (NNT)

Individual Level

Individual-level clinical significance

Efforts to come to conclusions about clinical significance at the individual level can be directly linked to EBP goals
Benchmark
The Reliable Change Index (RCI)
J-T approach
Patient acceptable symptom state (PASS)
minimal important change (MIC)

Critiquing Interpretations

Review discussion section of research reports for statements regarding:
Limitations
Sampling deficiencies
Practical constraints
Data quality problems
Methodology section
How limitations were considered in interpreting the results

Question

Which results are considered when interpreting the results of a quantitative research study? (Select all that apply.)

Magnitude of the effects

Underlying meaning of the results

Implication for nursing practice

Cost of the study

Credibility of the results

Answer

A, B, C, E

The interpretation of quantitative research results (the outcomes of the statistical analyses) typically involves consideration of (1) the credibility of the results; (2) precision of estimates of effects; (3) magnitude of effects; (4) underlying meaning of the results; (5) generalizability of results; and (6) implications for future research, theory development, and nursing practice. Cost of the study is not generally considered relevant to the quality of the results.