def combine_mean_std(row, metric, decimal_places):
    """ Merge mean and std column into a form like mean \pm std with mean and std rounded to a given decimal places. """
    m_avg = row[f'{metric}_mean']
    m_std = row[f'{metric}_std']
    testing_m_avg = ("{:."+str(decimal_places)+"f}").format(m_avg)
    testing_m_std = ("{:."+str(decimal_places)+"f}").format(m_std)

    val = '{avg} $\pm$ {std}'.format(avg=testing_m_avg, std=testing_m_std)
    return val