Match the cost estimating or budgeting technique to its expected accuracy / methodology

1 Rough Order of Magnitude (ROM) estimate

2 budgetary estimate

3 definitive estimate

4 analogous estimate or top-down estimate

5 bottom up estimate

6 Three point estimate

7 Parametric estimates

8 Hybrid estimate

A.	-50% to +100%
B.	total budget estimated by summing estimate of parts of project, total sum estimated last
C.	-5% to + 10%
D.	Taking good faith estimates prepared according to different theories, and throwing them together to build consensus, avoid surprises.
E.	Pessimistic, realistic and optimistic budgets are prepared, then averaged as follows: (1*pessimistic + 3*realistic + 1*optimistic)/5 in an attempt to match a "normal" distribution.
F.	budget estimated from a similar project, total sum allocated first, then assigned to parts of project
G.	Using statistical models based on normal distribution for various costs, to get a more nuanced view of possible low and high end and most likely costs. May also involve a multivariate model of factors influencing costs.
H.	-10% to +25%