Let's say I define random variable $\varphi$ is uniformly distributed between $[0,2\pi).$
I then define Random process $y(t)=\sin(2\pi t+\varphi)$
Is this process SSS? For now, let's assume that the definition of SSS is that the PDF is not conditional on $t$
What about
$$z(t)=\sin^2\left(2\pi t+\varphi\right) \text{ ?}$$