In this exercice, we are required to complete a statement about the use of schedule and cost indexes over the absolute values of SV and CV$.$

$2$

Let's start by understanding those concepts:

The Schedule Performance Index is calculated by dividing the Earned Value $($EV$)$ by the Planned Value $($PV$).$ The SPI represents the efficiency of the project in terms of schedule.

The Cost Performance Index is calculated by dividing the Earned Value $($EV$)$ by the Actual Cost $($AC$).$ The CPI represents the efficiency of the project in terms of cost$.$

$3$

Indeed, practitioners sometimes prefer to use schedule and cost indexes over the absolute values of SV and CV$,$ because indexes are considered efficiency ratios.

Efficiency ratios provide a measure of how effectively resources are being utilized to achieve project objectives.

$4$

In conclusion, indexes are preferred because they offer better insights on the efficiency.