def get_z_sample(xbar, mu, SE):
    """
    Return the z-score of a sample, from a sampling distribution.

    Parameters
    ----------
    * xbar: mean of the current sample.
    * mu: mean of the population from where the sample is drawn.
    * SE: standard error of the sampling distribution (population SD / root(population size))

    Returns
    -------
    The z-score of the sample with mean less than or equal to xbar.
    Given by (xbar - mu) / SE.
    """
    return (xbar-mu) / SE