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Table 4 Effect of study length on the power of the study

From: Tailoring and evaluating an intervention to improve shared decision-making among seniors with dementia, their caregivers, and healthcare providers: study protocol for a randomized controlled trial

Scenario Estimated power Threshold of statistical significance HCEQ Standard Deviation Minimum detectable difference (Cohen’s effect size of 0.6) Intra-cluster correlation Adjusted standard deviation Number of clusters (clinics) Totalsample size Study length (months) Mean number of patients per clinic
1 0.519 0,05 2.46 1.476 0,02 2.65 6 54 1 9
2 0.76 0,05 2.46 1.476 0,02 2.85 6 108 2 18
3 0.88 0,05 2.46 1.476 0,02 2.98 6 162 3 27
4 0.92 0,05 2.46 1.476 0,02 3.21 6 216 4 36
5 0.948 0,05 2.46 1.476 0,02 3.37 6 270 5 45
6 0.963 0,05 2.46 1.476 0,02 3.53 6 324 6 54