Evidence-Based Practice / Unit 6 EBP 0850 worked example, 60 to 90 seconds
Reading the Numbers in a Study
The idea
The technique: find the four cells, check the counts add up, identify whether the outcome is dichotomous or continuous, then read the absolute risks, their difference, the ratio, and the number needed to treat — weighing the absolute figures, not the relative ones, against this patient.
In practice
A trial's outcome counts located and summed against enrolment. Outcome dichotomous. Absolute risks calculated for each group; the difference taken; the ratio taken; the number needed to treat derived from the absolute difference. The relative reduction noted as the figure the abstract led with. The absolute figures carried into the decision, the relative one into the record of how the result was reported.
Where people slip
Do the absolute measures first. Reading the relative figure first sets an impression the absolute figures then have to argue against.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Builds on
- 0823N and n
- 0824Do the n Values Sum to N?
- 0825Dichotomous Data
- 0828Magnitude of Effect
- 0829The Two-by-Two Table
- 0830Absolute Risk
- 0831Risk Difference
- 0834Relative Risk
- 0836Relative Risk Reduction
- 0837Same Data, Two Impressions
- 0839Odds
- 0842Number Needed to Treat
- 0844Absolute Measures Carry Baseline Risk
- 0848Adverse Effects Enter the Same Judgement
Unlocks
- Nothing yet depends on this.
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