Table 2 

Uncertainty analysis 

Parameters 
Values 
Uncertainty distribution 
Sources and assumptions 


Height, weight of participants 
Mean, SE^{a} 
Normal^{b} 
[19] 
No. local governments making submissions 
296, 370, 444^{c} 
Triangular^{d} 
Estimate 
% nonVictorian local governments participating 
0.4, 0.5, 0.6^{3} 
Triangular^{d} 
Estimate based on VicHealth figures for Victoria 
No. participating schools per local government 
4, 1^{b} 
Normal^{b} 
VicHealth 
Persons attending recruitment evening per school 
10, 15, 20^{c} 
Triangular^{d} 
Estimate 
Volunteers recruited per school 
7,3^{b} 
Normal^{b} 
Estimate 
WSB per school 
1, 1.6, 3^{c} 
Triangular^{d} 
Min, max  estimates; most likely  Vic Health 
Volunteers trained per WSB 
2, 4, 6^{c} 
Triangular^{d} 
Min, max  estimates; most likely  VicHealth guidelines 
Average number of children per WSB 
3, 7, 12^{c} 
Triangular^{d} 
Estimate 
Extra minutes spent on walking 
6, 28.3, 84^{c} 
Triangular^{d} 
[15] 
No. of days of WSB per week per child 
0.5, 1, 5^{c} 
Triangular^{d} 
Mean [15] 
No. weeks of intervention effect per year 
35, 40^{e} 
Uniform^{f} 
Estimate 
Increased METS from walking 
1.5, 2.5, 3^{c} 
Triangular^{d} 
[13] 
Factor to convert % change in energy balance to % change in body weight 
0.38, 0.45, 0.51^{c} 
Triangular^{d} 
[14] 
% children enrolled in WSB not walking previously 
25%, 50%, 75%^{c} 
Triangular^{d} 
Estimate 
Local government officer time (days per week) 
2, 3, 4^{c} 
Triangular^{d} 
Estimate based on personal communication VicHealth 
Oncost loading on national and state coordinator salaries 
50%, 60%, 70%^{c} 
Triangular^{d} 
Estimate 
Oncost loading on teachers, local government officer salaries 
20%, 30%, 40%^{c} 
Triangular^{d} 
Estimate 
School liaison officer time/coordinator time (hours per week) 
1, 4^{e} 
Uniform^{f} 
Estimates based on personal communication VicHealth 
Volunteer time (minutes per journey/day) 
12, 40, 80^{c} 
Triangular^{d} 
[15] 
Manual cost 
$40 ± 20%^{c} 
Triangular^{d} 
Estimate 
Kit bags  cost 
$50 ± 20%^{c} 
Triangular^{d} 
Estimate 
Special events, theme days etc. 
$100, $300, $500^{c} 
Triangular^{d} 
Estimate 


^{a }These values inserted separately for height and weight of boys and girls in 59 and 1011 year age groups. ^{b }In a normal distribution, values are distributed in a normal bellshaped around the mean. The distribution is based on the mean and the standard error. ^{c }Values are minimum, most likely and maximum. ^{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). ^{e }Values are minimum and maximum. ^{f }In a uniform distribution, every value in the specified range has an equal probability of being chosen in each iteration of the simulation. WSB Walking School Bus; SE Standard Error; METS metabolic equivalent units Source: ACEObesity project 

Moodie et al. International Journal of Behavioral Nutrition and Physical Activity 2009 6:63 doi:10.1186/14795868663 