Revival: Biological Effects of Low Level Exposures to Chemical and Radiation (1992)

BIOSTATISTICAL APPROACHES TO ASSESSMENT 135

Table 7.6. Probability of Observing a Significantly Lower Risk in an Exposed Group, by Relative Risk and Expected Number of Cases in the

Exposed Group When the Relative Risk is Unity

Relative Risk

Expected Cases

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

2

0

0

0

0

0

0

0

0

0

0

4

67

45

30

20

14

9

6

4

3

2

6

88

66

46

31

20

13

8

5

3

2

8

95

78

57

38

24

14

8

5

3

1

10

98

86

65

43

27

15

8

4

2

1

12

100

96

84

65

45

28

16

8

4

2

14

100

98

87

67

45

27

14

7

3

1

16

100

99

94

80

59

38

21

11

5

2

18

100

100

95

81

59

36

19

9

4

2

20

100

100

98

89

70

46

26

13

5

2

22

100

100

98

89

69

44

24

11

4

2

24

100

100

99

94

77

53

30

14

6

2

26

100

100

100

96

84

61

36

17

7

2

28

100

100

100

96

83

58

33

15

6

2

30

100

100

100

98

88

65

38

18

7

2

32

100

100

100

98

87

63

36

16

5

2

34

100

100

100

99

90

69

41

19

7

2

36

100

100

100

99

93

74

46

21

8

2

38

100

100

100

99

93

72

43

19

6

2

40

100

100

100

100

95

77

47

22

7

2

42

100

100

100

100

96

81

52

24

8

2

44

100

100

100

100

96

79

49

22

7

2

46

100

100

100

100

97

83

53

24

8

2

48

100

100

100

100

98

86

57

27

9

2

50

100

100

100

100

99

88

61

30

10

2

Note:

Rounded to nearest percent. Test statistic is observed Poisson-distributed count of cases in exposed group. Nominal probability of 2.5% in lower tail.