is given by the table.

A *test* for a signed probability space $S = (\Omega,{\mathcal P})$ is given by (and, mathematically speaking, can be identified with) a partition of $\Omega$ into parts of nonnegative probability.

An *execution* of a test picks out one of its parts. The example above explicitly exhibits three tests.

> [[Q: ]{}]{}Normally, in traditional probability theory, an execution of a probability trial picks out an outcome $\omega$ with probability ${\mathcal P}(\omega)$. Why don’t you do that in general? Require that only outcomes of nonnegative probability are picked out.
>
> [[A: ]{}]{}The proposed test is impossible in the case of nontraditional probability distribution. Notice that, in the example, the probability of the event $e^+ = \{\omega\in\Omega: {\mathcal P}(\omega)\ge0\}$ is more than 1. What would it mean to pick an outcome from $e^+$ according to a distribution with total probability $>1$? Our definition of test intends to reflect measurements in quantum mechanics.

Observation frames {#sec:frame}
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Our goal in this section is to formalize the notions of an observable event and a coobservable set of events. Intuitively, a set $E$ of events is coobservable if there is a test $\tau_E$ that allows us to observe, for all 