  In this paper we introduce the three main notions of probability used by
physicists and discuss how these are to be used when invoking spacelike
separated observers in a relativistic format. We discuss a standard EPRB
experiment and concentrate upon problems of the interpretation of
probabilities. We promote a particularly conservative interpretation of this
experiment (which need not invoke an objective notion of collapse) where
probabilities are, tentatively, passively Lorentz invariant. We also argue that
the Heisenberg picture is preferable in relativistic situations due to a
conflict between the Schrodinger picture and passive Lorentz transformations of
probabilities. Throughout most of this paper we discuss the relative frequency
interpretation of probability as this is most commonly used. We also introduce
the logically necessary notion of `prior-frequency' in discussing whether the
choice by an observer can have any causal effect upon the measurement results
of another. We also critically examine the foundational use of relative
frequency in no-signalling theorems. We argue that SQT and SR are
probabilistically compatible, although we do not discuss whether they are
compatible on the level of individual events.
