In general, why is it NOT a good idea to estimate the testing effort based only on a percentage of development effort?

Topic 12, Scenario 7 "Test Estimation"

You have been contracted to manage the acceptance testing of a new computer-based reservation system for a travel agency. You have provided an approximate budget estimate for the testing project based on previous experience with similar sized projects. However, the management of the parent company of the travel agency will not commit to the budget until detailed cost estimates are provided.

The reservation system is being developed by a third party However, detailed specifications of the software are available, as well as an estimate of the total effort that will be spent in developing the software. The software is to be delivered in four increments, and the functionality to be delivered in each increment has already been agreed on.

In general, why is it NOT a good idea to estimate the testing effort based only on a percentage of development effort? Identify THREE valid reasons. 1 credit
A . The quality of the development estimate may be poor.
B . In general bottom-up estimation is always better than top-down estimation.
C . The percentage based technique only applies to the V life cycle model.
D . Using the same percentage every time does not address the level of risk of the application to be tested.
E . The maturity of the organization, e.g. the quality of the test basis, quality of development testing, configuration management, availability of test tools, also influence the effort needed for testing.
F . It builds on large set of historical data
G . The result is almost always a too low estimate for the required test effort

Answer: A,D,E