There are two commonly discussed forms of quantum turbulence in superfluid above 1 K: in one there is a random tangle of quantized vortex lines, existing in the presence of a nonturbulent normal fluid; in the second there is a coupled turbulent motion of the two fluids, often exhibiting quasiclassical characteristics on scales larger than the separation between the quantized vortex lines in the superfluid component. The decay of vortex line density, , in the former case is often described by the equation , where is the quantum of circulation and is a dimensionless parameter of order unity. The decay of total turbulent energy, , in the second case is often characterized by an effective kinematic viscosity, , such that . We present values of derived from numerical simulations and from experiment, which we compare with those derived from a theory developed by Vinen and Niemela. We summarize what is presently known about the values of from experiment, and we present a brief introductory discussion of the relationship between and , leaving a more detailed discussion to a later paper.