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. Author manuscript; available in PMC: 2015 Jan 29.
Published in final edited form as: Epidemiology. 2014 Nov;25(6):889–897. doi: 10.1097/EDE.0000000000000160

Table 1.

Estimating risk under interventions using the g-formula with the hypothetical example given in methods section of the main text.

G-formula component Value
Conditional probabilities
First 5 years PR(exposed): 0.5
Risk among exposed: 0.025
Risk among unexposed: 0.025
Last 5 years Pr(exposed): 0.5
Risk among exposed: 0.060
Risk among unexposed: 0.051
Risk under interventions
Observed/Natural course 0.051*(1/2)*(1-0.025*(1/2)) + 0.025*(1/2) +
0.060*(1/2)*(1-0.025*(1/2)) + 0.025*(1/2) = 0.080
Always exposed 0.051*(0)*(1-0.025*(0)) + 0.025*(0) +
0.060*(1)*(1-0.025*(1)) + 0.025*(1) = 0.084
Never exposed 0.051*(1)*(1-0.025*(1)) + 0.025*(1) +
0.060*(0)*(1-0.025*(0)) + 0.025*(0) = 0.075
Expose if survive to year 5 0.051*(0)*(1-0.025*(0)) + 0.025*(1/2) +
0.060*(1)*(1-0.025*(1)) + 0.025*(1/2) = 0.084