Table 2

Uncertainty analysis

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


a These values inserted separately for height and weight of boys and girls in 5-9 and 10-11 year age groups.

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.

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: ACE-Obesity project

Moodie et al. International Journal of Behavioral Nutrition and Physical Activity 2009 6:63   doi:10.1186/1479-5868-6-63

Open Data