An example of a necessary tool when coding subjective beliefs into probabilities: correspondence between ordinary language expressions and quantitative probabilities (from F. Mosteller and C. Youtz (1990). Quantifying Probabilistic Expressions, Statistical Science, 5, 1, 2-34.)



Expression

lower point

upper point


Expression

lower point

upper point








Always

99.6

99.8


Less often than not

34.8

42.7

Almost always

89.7

95.2


Not often

10.3

24.8








Certain

98.7

99.8


Not very often

5.3

19.8

Almost certain

87.5

95.0


Possible

7.5

50.2





Impossible

0.2

0.5

Very frequent

75.3

89.7


High chance

77.5

89.1

Frequent

60.0

75.3


Better than even chance

53.3

60.2

Not frequent

32.7

57.3


Even chance

49.7

50.2

Infrequent

10.1

22.6


Less than an even chance

45.0

39.6

Very infrequent

3.6

10.0


Poor chance

8.4

19.7





Low chance

5.0

12.8

Very high probability

89.8

95.2


Liable to happen

59.8

77.7

High probability

77.1

87.2


Might happen

19.9

50.1

Moderate probability

40.1

58.7





Low probability

7.8

22.3


Usually

65.6

82.2

Very low probability

1.9

7.6


Unusually

9.9

26.1





Sometimes

17.5

35.0

Very likely

80.1

90.2


Once in a while

9.9

22.4

Likely

62.6

77.6


Not unreasonable

23.5

52.6

Unlikely

9.8

22.7


Occasionally

12.5

27.7

Very unlikely

2.7

9.8


Now and then

9.8

25.0








Very probable

81.5

90.4


Seldom

7.4

17.5

Probable

64.7

77.7


Very seldom

3.2

7.7

Improbable

7.6

22.3





Very improbable

1.5

7.5


Rarely

3.6

10.0





Very rarely

1.2

5.0

Very often

77.5

89.9


Almost never

1.2

4.6

Often

65.0

75.4


Never

0.1

0.4

More often than not

57.1

60.4


Never

0.1

0.4

As often as not

49.8

50.3