Table 2 Ratings for frequency of occurrence, detectability and severity

Frequency of occurrence of failure mode

Once a year

1

Once a month

2

Once a week

3

Once a day

4

Several times a day

5

Detectability of failure mode

 ≥ 90%

1

 ≥ 75%

2

 ≥ 50%

3

 ≥ 25%

4

 ≥ 10%

5

0–9%

6

Severity of the effect of the failure mode

Slight annoyance: may affect the cancer treatment system

1

Moderate system problem: may affect the patient

2

Major system problem: may affect the patient

3

Minor injury

4

Major injury

5

Terminal injury or death

6