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What is the correct range of rough order of magnitude est?

Posted: Mon Aug 25, 2014 6:36 am
by nagarwal
Different books provide different range for order of magnitude estimates. Like as per Rita''s book:

Rough Order of Magnitude is = -25 - +75
Budget Estimate = -10 - +25
Definitive Estimate = +/- 10

Can you please comment if these are accurate? If not, is there a way to deal with them?

Re: What is the correct range of rough order of magnitude es

Posted: Mon Aug 25, 2014 7:16 am
by saket
You have to just get that ROM will be high ... and PMBOK has just shared some example of it which is not necessarily true in your organization, I do not expect exam asking about what should be the exact % range for ROM, if it ask... look at the option and pick the once is is near −25% to +75%

PMBOM Guide Page No 201
For example, a project in the initiation phase may have a rough order of magnitude (ROM) estimate in the range of −25% to +75%. Later in the project, as more information is
known, definitive estimates could narrow the range of accuracy to -5% to +10%. In some organizations, there are guidelines for when such refinements can be made and the degree of confidence or accuracy that is expected.

Re: What is the correct range of rough order of magnitude es

Posted: Mon Aug 25, 2014 7:42 am
by nagarwal
Thx! That's really helpful.

Re: What is the correct range of rough order of magnitude es

Posted: Wed Aug 27, 2014 3:17 am
by vivkalia
saket wrote:You have to just get that ROM will be high ... and PMBOK has just shared some example of it which is not necessarily true in your organization, I do not expect exam asking about what should be the exact % range for ROM, if it ask... look at the option and pick the once is is near −25% to +75%

PMBOM Guide Page No 201
For example, a project in the initiation phase may have a rough order of magnitude (ROM) estimate in the range of −25% to +75%. Later in the project, as more information is
known, definitive estimates could narrow the range of accuracy to -5% to +10%. In some organizations, there are guidelines for when such refinements can be made and the degree of confidence or accuracy that is expected.


Rita's book says the ROM is +/- 50%.
Saket, are you referring from the PMBOK?
Which one should be taken if both the choices are shown?

Re: What is the correct range of rough order of magnitude es

Posted: Wed Aug 27, 2014 5:51 am
by saket
You should not get such questions in real exam... it can only come in practice tests .... so we need to understand the intent of ROM and PMBOK range is an example... same way rita is also an example...