Lack of reasonable schedule caused by the project is lagging the main reason, it affects all other factors combined ratio is greater
Causes
. A rigorous scientific estimation techniques do not, the lack of effective research, built on the false assumption: everything will run well
b. the lack of progress tracking and oversight
c. May that man can be interchanged, schedule and workload is not equal
Optimism programmer
Man-month relationship
. A relationship between staff and time - task completely decomposed (no manual work such as exchange of wheat harvesting, it almost impossible in system programming)
. B relations personnel and time - not completely break down tasks (woman gave birth to a human life takes 10 months, can not be reduced by increasing the staff at any time of the 10 months)
. C relations personnel and time - decomposable task requires communication (Communication: training and mutual exchanges)
d relations personnel and time - the complex relationship between tasks (work practice / communication is very large)
System test
Task scheduling software, author of many years of practical experience: [Author: US Small Frederick Brooks, he served IBM, engaged in R & D management]
1/3 plan
1/6 coding
1/4 component testing and early system testing
1/4 system test, all components have been completed
Prior to the study of traditional project schedule, I found very few projects allow half the time allocated for the test, but the test most projects is actually spent in the general progress of time, many of them projects in system testing but also to maintain progress.
It is not sufficient time to test the system most likely lead to catastrophic consequences
The new staffing arrangements for the project behind schedule will only make progress more look behind