dimensions (Table 9) consider important aspects of the evidence supporting a particular intervention and include three main domains: strength of the evidence, size of the effect and relevance of the evidence. The first domain is derived directly from the literature identified as informing a particular intervention. The last two require expert clinical input as part of its determination. Table : Evidence dimensions Type of evidence Definition Strength of the evidence The study design used, as an indicator of the degree to which bias has been eliminated by design.* Level The methods used by investigators to minimise bias within a study design. Quality The p-value or, alternatively, the precision of the estimate of the effect. It reflects the degree of Statistical precision certainty about the existence of a true effect. The distance of the trial estimate from the value and the inclusion of only clinically important ‘null’ Size of effect effects in the confidence interval. The usefulness of the evidence in clinical practice, particularly the appropriateness of the outcome Relevance of evidence measures used. Strength of the evidence The trial sub-domains (level, quality and statistical precision) are collectively a measure of the strength of the evidence. The of evidence’ reflects the effectiveness of a study design to answer a particular ‘level research question. Effectiveness is based on the probability that the design of the study has reduced or eliminated the impact of bias on the results. The NHMRC evidence hierarchy provides a ranking of various study designs (‘levels of evidence’) by the type of research question being addressed (Table 10).
dimensions (Table 9) consider important aspects of the evidence supporting a particular intervention and include three main domains: strength of the evidence, size of the effect and relevance of the evidence. The first domain is derived directly from the literature identified as informing a particular intervention. The last two require expert clinical input as part of its determination. Table : Evidence dimensions Type of evidence Definition Strength of the evidence Level Quality Statistical precision The study design used, as an indicator of the degree to which bias has been eliminated by design.* The methods used by investigators to minimise bias within a study design. The p-value or, alternatively, the precision of the estimate of the effect. It reflects the degree of certainty about the existence of a true effect. Size of effect The distance of the estimate from the ‘null’ value and the inclusion of only clinically important effects in the confidence interval. Relevance of evidence The usefulness of the evidence in clinical practice, particularly the appropriateness of the outcome measures used. Strength of the evidence The sub-domains (level, quality and statistical precision) are collectively a measure of the strength of the evidence. The ‘level of evidence’ reflects the effectiveness of a study design to answer a particular research question. Effectiveness is based on the probability that the design of the study has reduced or eliminated the impact of bias on the results. The NHMRC evidence hierarchy provides a ranking of various study designs (‘levels of evidence’) by the type of research question being addressed (Table 10). trial trial
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