def q_function_approximation(x: str = 'x') -> str:
    """
    Returns a string representing the Stirling approximation for the Q function.

    **Parameters**

    - `x`: str

        The argument of the Q function.

    **Returns**

    `out`: str

        TeX compatible string.
    """

    return f'Q({x}) \\approx \\frac{{1}}{{2}} e^{{-\\frac{{{x}^2}}{{2}}}}'