For the function \( f(x)=\sin x+3x-\dfrac{2}{\pi}(x^{2}+x) \), where \( x\in\left[0,\dfrac{\pi}{2}\right] \), consider the following two statements:
(\(I\)) \( f \) is increasing in \( \left(0,\dfrac{\pi}{2}\right) \).
(\(II\)) \( f' \) is decreasing in \( \left(0,\dfrac{\pi}{2}\right) \).
Between the above two statements,
