The boxplot shows the four different treatments. The membrane devices have the largest variation (undesirable for a measurement instrument). Also their measurements seem to be contradicted by all other three devices.

The devices show wide differences in their measurements: While the ``Filter'' device reports measurments between 15 and 28, the ``Membrane'' device recorded between around 25 and 45. We would need to know the true level of radiation which they were exposed to in order to judge which device is actually more reliable. The ``Membrane'' device shows a remarkable wide range of measurements.

In MINITAB use the command dotplot to get a similar plot:

 MTB >  dotplot 'FILTER' 'MEMB' 'CUP' 'BADGE'

                                  :               :   .
              :   .       .   .   :       :       :   :   .   .
          +---------+---------+---------+---------+---------+-------FILTER
       15.0      17.5      20.0      22.5      25.0      27.5

              .     . :       .   . : . .   . : :       . . : .
          +---------+---------+---------+---------+---------+-------MEMB
       20.0      25.0      30.0      35.0      40.0      45.0
                 .    .    .                   .    .
                 :    :    :    :    .         :    :         :
           -+---------+---------+---------+---------+---------+-----CUP
         26.0      28.0      30.0      32.0      34.0      36.0
                                                     :    .
             .         .    :    .    :    :    :    :    :    :
           -------+---------+---------+---------+---------+---------BADGE
               22.0      24.0      26.0      28.0      30.0      32.0