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Table 1 Sample size calculations

From: Effectiveness of the head CT choice decision aid in parents of children with minor head trauma: study protocol for a multicenter randomized trial

Outcome (n = 950)

Usual care*

Decision aid*

Difference

Power

Parent knowledge

44%

60%

16%

>99%

Parent engagement in the decision-making process

7.0 (5.5)

27.0 (8.2)

20.0

>99%

Decisional conflict †

36 (19)

21 (21)

15

>99%

Trust in the physician

79 (20.0)

84 (20.0)

4.1

86%

Parent satisfaction with the decision made (% agree or strongly agree they are satisfied)

70.0 (26)

80 (26.0)

10.0

>99%

Safety (clinically-important traumatic brain injury) ‡

0.9%

0.9%

0%

82.5%

Proportion of children who undergo head CT §

49%

34%

15%

95%

Healthcare utilization

8.3 (0.8)

6.8 (0.7)

1.5

>99%

  1. *Estimates were determined from our completed randomized trial for adult patients presenting to the emergency department with chest pain and are presented as mean (standard deviation) or percentage.
  2. †Lower decision conflict scores indicate less conflict experienced by patients related to feeling uninformed.
  3. ‡ Non-inferiority, one-sided test with alpha = 0.05 with a maximum difference of 2%. Baseline rates determined from the PECARN prediction rule study.
  4. § Obtained from the rate of CT scan in the moderate risk group of patients in the PECARN prediction rule study.
  5. CT, computed tomography.