This brief is concerned with the problem of periodic event-triggered dynamic output feedback (DOF) dissipative control with a probabilistic detection of event-triggering conditions. By employing the input-delay approach, the stochastically periodic event-triggered control (SPETC) system is modeled as a probabilistic delay closed-loop system. Then by utilizing tools from Lyapunov functional and stochastic system theory, sufficient conditions are derived in terms of linear matrix inequalities to guarantee the closed-loop system to be strictly $(\mathcal {Q}, \mathcal {S}, \mathcal {R})$ - $\alpha $ -dissipative. The effectiveness of the design procedure is illustrated numerically by conducting simulations on a second order series RLC circuit example.