Briefly explain the primary function of a statement of purpose indicating the most useful way to ...

(Answers may vary.) A statement of purpose defines why you are preparing your report and what you plan to deliver in the report. The most useful way to phrase your purpose statement is to begin with an infinitive phrase (to plus a verb), which helps pin down your general goal (to inform, to identify, to analyze, and so on).

The purpose statement to help a company find ways to reduce the amount it spends on employee health and dental benefits is: To identify ways to help reduce expenses on employee health and dental benefits.