age             plasma
    0             13.44
    0             12.84
    0             11.91
    0             20.09
    0             15.60
  1.0             10.11
  1.0             11.38
  1.0             10.28
  1.0              8.96
  1.0              8.59
  2.0              9.83
  2.0              9.00
  2.0              8.65
  2.0              7.85
  2.0              8.88
  3.0              7.94
  3.0              6.01
  3.0              5.14
  3.0              6.90
  3.0              6.77
  4.0              4.86
  4.0              5.10
  4.0              5.67
  4.0              5.75
  4.0              6.23