brand power time  y
    1     1     1  73.8
    1     1     1  65.5
    1     1     2  70.3
    1     1     2  91.0
    1     1     3  72.7
    1     1     3  81.9
    1     2     1  70.8
    1     2     1  75.3
    1     2     2  78.7
    1     2     2  88.7
    1     2     3  74.1
    1     2     3  72.1
    2     1     1  73.7
    2     1     1  65.8
    2     1     2  93.4
    2     1     2  76.3
    2     1     3  45.3
    2     1     3  47.6
    2     2     1  79.3
    2     2     1  86.5
    2     2     2  92.2
    2     2     2  84.7
    2     2     3  66.3
    2     2     3  45.7
    3     1     1  62.5
    3     1     1  65.0
    3     1     2  50.1
    3     1     2  81.5
    3     1     3  51.4
    3     1     3  67.7
    3     2     1  82.1
    3     2     1  74.5
    3     2     2  71.5
    3     2     2  80.0
    3     2     3  64.0
    3     2     3  77.0