head         weight
            1            15.70
            2            15.69
            3            15.75
            4            15.68
            5            15.65
            1            15.68
            2            15.71
            3            15.82
            4            15.66
            5            15.60
            1            15.64
            3            15.75
            4            15.59
            1            15.60
            3            15.71
            3            15.84