The parameters of a two-dimensional dusty plasma consisting of six, 9 μm diameter particles trapped inside a radio frequency (rf) plasma sheath have been measured as a function of rf power in a 13.5 mtorr (1.8 Pa) argon discharge. The center-of-mass and breathing frequencies are found by projecting the cluster’s Brownian motion onto the associated normal mode. The center-of-mass frequency (i.e., radial confinement) is insensitive to rf power. The Debye shielding parameter κ, as found from the breathing frequency, increases from ≈0.5 to 2 as the square root of rf power. The Debye length decreases from ≈2.7 to 0.7 mm as the inverse of the square root of rf power. The average particle charge q≈−17 000e is effectively independent of rf power. These results are consistent with an electron temperature that is independent of rf power and an ion density that is directly proportional to rf power, where the Debye length is determined by the ion density in combination with the electron temperature.