def cols_to_drop(statistic, threshold, greater):
    """
    Compiles a list of columns to be dropped by drop_cols(), using the given
    summary statistics.

    Parameters:
    _________________
    statisic:        Statistic to use for feature evaluation; should have
                     <lr_model>.summary.<statistic>
    threshold:       (float) Number used as the threshold for feature evaluation
    greater:         (bool) If true, dop columns which are greater than the
                     given threshold; otherwise, drop columns which are less
                     than the given threshold

    Returns:
    _________________
    cols_list: (list) list of columns to be dropped by drop_cols()
    """
    cols_list = []
    if greater:
        for val in range(len(statistic)):
            if statistic[val] >= threshold:
                cols_list.append("X{}".format(val+1))
    else:
        for val in range(len(statistic)):
            if statistic[val] <= threshold:
                cols_list.append("X{}".format(val+1))
    return cols_list