Why intermediate COCOMO is expected to give more accurate estimates compared to the basic COCOMO?

The basic COCOMO

model assumes that effort and development time are
functions of the product size alone. However, a host of other project parameters besides the product size affect the effort required to develop the product as well as the development time. Therefore, in order to obtain an accurate estimation of the effort and project duration, the effect of all relevant parameters must be taken into account. The intermediate COCOMO

model recognizes this fact and refines the initial estimate obtained using the basic COCOMO

expressions by using a set of 15 cost drivers (multipliers) based on various attributes of software development. That's why intermediate COCOMO

is expected to give more accurate estimates compared to the basic COCOMO