Biomedical Engineering Reference
In-Depth Information
Table 6.10: Example of a completed criteria Assessment for Measurement of Temperature
Specification Item
Mercury
Thermometer
Infrared
Camera
Thermocouple
Temperature
Sensitive Gels
Integrated
Circuit Chip
1. Measure temperature from
0-40°C
10
10
10
10
10
2. Not toxic
0
10
8
7
9
3. Reusable after suitable
sterilization
10
10
9
1
2
4. Low power consumption
10
1
4
10
8
5. Low purchase cost
0
1
5
8
7
6. Ability to transmit data
4
10
8
6
9
Total Score
34
42
44
42
45
the individual rows are weighted relative to their importance. For example there may
be a specification requirement for the device to be blue, but compared with another
requirement stating it should be nontoxic this is relatively minor. Hence to give the rows
the importance they deserve it is common to give them a weighting in either decimal
or percentage terms. The easiest way to do this is to rank them with the most important
being ranked first, and the least important being last. Once again, the best way to obtain
this ranking is to pass the list to a group and let them, individually, do the ranking. It is
then relatively easy to assimilate the marks to obtain a syndicated, average ranking table.
This is also a very good way to include customer/end-user input. To calculate the rank we
use the formula
i
05
.
(6.1)
W1
1
n
Alternatively you can just attribute the weighting as
ni
n
%
(6.2)
W2
100
1
But this means the last one always has a zero ranking. Just a simple reversal of the rank (see
W3) often works.
So for example the weighting of 6.9 may be as in
Table 6.11
.
Note that I have made items 4 and 6 equal at 4.5, which is midway between 4 and 5 (i.e., they
share an equal rank). If there were three sharing it would be 4.33; four sharing 4.25, and so
on. The next rank number is then back to sequence, i.e., 6 and not restarting at 5. Hence for
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