Fluctuations and correlations of conserved quantities (baryon number, strangeness, and charge) can be used to probe phases of the strongly interacting QCD matter and the possible existence of a critical point in the phase diagram. The cumulants of the multiplicity distributions related to these conserved quantities are expected to be sensitive to possible increased fluctuations near a critical point. In this report, we present the measurements of the cumulants of net-proton multiplicity distributions from Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4 (up to fourth order) and 200 GeV (up to sixth order) as measured by the STAR experiment at RHIC. Multi-particle correlation functions will also be presented.

The higher order cumulants are also very sensitive to experimental artifacts that one has to deal with in the analyses of heavy-ion collision data. We demonstrate a data-driven approach to measure the cumulants of event-by-event distributions of physical variables using large samples of AMPT events. Our approach investigates the corrections for multiplicity-dependent detector response and efficiency variations. The comparison of the various correction approaches should provide important guidance towards a reliable experimental determination of the multiplicity cumulants.