obs      y         x1
        1     10.98      35.3
        2     11.13      29.7
        3     12.51      30.8
        4      8.4       58.8
        5      9.27      61.4
        6      8.73      71.3
        7      6.36      74.4
        8      8.5       76.7
        9      7.82      70.7
       10      9.14      57.5
       11      8.24      46.4
       12     12.19      28.9
       13     11.88      28.1
       14      9.57      39.1
       15     10.94      46.8
       16      9.58      48.5
       17     10.09      59.3
       18      8.11      70
       19      6.83      70
       20      8.88      74.5
       21      7.68      72.1
       22      8.47      58.1
       23      8.86      44.6
       24     10.36      33.4
       25     11.08       28.6