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Table 2 Uncertainty analysis

From: Cost-effectiveness of active transport for primary school children - Walking School Bus program

Parameters Values Uncertainty distribution Sources and assumptions
Height, weight of participants Mean, SEa Normalb [19]
No. local governments making submissions 296, 370, 444c Triangulard Estimate
% non-Victorian local governments participating 0.4, 0.5, 0.63 Triangulard Estimate based on VicHealth figures for Victoria
No. participating schools per local government 4, 1b Normalb VicHealth
Persons attending recruitment evening per school 10, 15, 20c Triangulard Estimate
Volunteers recruited per school 7,3b Normalb Estimate
WSB per school 1, 1.6, 3c Triangulard Min, max -- estimates; most likely -- Vic Health
Volunteers trained per WSB 2, 4, 6c Triangulard Min, max -- estimates; most likely -- VicHealth guidelines
Average number of children per WSB 3, 7, 12c Triangulard Estimate
Extra minutes spent on walking 6, 28.3, 84c Triangulard [15]
No. of days of WSB per week per child 0.5, 1, 5c Triangulard Mean [15]
No. weeks of intervention effect per year 35, 40e Uniformf Estimate
Increased METS from walking 1.5, 2.5, 3c Triangulard [13]
Factor to convert % change in energy balance to % change in body weight 0.38, 0.45, 0.51c Triangulard [14]
% children enrolled in WSB not walking previously 25%, 50%, 75%c Triangulard Estimate
Local government officer time (days per week) 2, 3, 4c Triangulard Estimate based on personal communication VicHealth
On-cost loading on national and state coordinator salaries 50%, 60%, 70%c Triangulard Estimate
On-cost loading on teachers, local government officer salaries 20%, 30%, 40%c Triangulard Estimate
School liaison officer time/coordinator time (hours per week) 1, 4e Uniformf Estimates based on personal communication VicHealth
Volunteer time (minutes per journey/day) 12, 40, 80c Triangulard [15]
Manual cost $40 ± 20%c Triangulard Estimate
Kit bags - cost $50 ± 20%c Triangulard Estimate
Special events, theme days etc. $100, $300, $500c Triangulard Estimate
  1. a These values inserted separately for height and weight of boys and girls in 5-9 and 10-11 year age groups.
  2. b In a normal distribution, values are distributed in a normal bell-shaped around the mean. The distribution is based on the mean and the standard error.
  3. c Values are minimum, most likely and maximum.
  4. d In a triangular distribution, the greatest probability of being chosen is the value representing the top of the triangle (i.e. the most likely value), while the probability of other values being chosen tapers off towards the extremes of the base of the triangle (i.e. the minimum and maximum values).
  5. e Values are minimum and maximum.
  6. f In a uniform distribution, every value in the specified range has an equal probability of being chosen in each iteration of the simulation.
  7. WSB Walking School Bus; SE Standard Error; METS metabolic equivalent units
  8. Source: ACE-Obesity project