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USEFUL STUFF SAMPLE DATA DEVIATION TABLE

Sample deviation (confidence interval) depends on 3 factors:

  1. Sample size
  2. Confidence level
  3. Parameter value in sample

Confidence intervals decrease (sample deviation decreases) when

  • Sample size is increased
  • Confidence level is decreased
  • When the parameter value is close to 0% or 100% (confidence interval is biggest at 50%)

95% confidence level is the most widely accepted standard for evaluating study data deviation.


Sample size

Confidence level 95%

Parameter value, %

5.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

95.0

50

Low

0.8

3.3

10.0

17.9

26.4

35.5

45.2

55.4

66.3

78.2

84.8

High

15.2

21.8

33.7

44.6

54.8

64.5

73.6

82.1

90.0

96.7

99.2

100

Low

1.6

4.9

12.7

21.2

30.3

39.8

49.7

60.0

70.8

82.4

88.7

High

11.3

17.6

29.2

40.0

50.3

60.2

69.7

78.8

87.3

95.1

98.4

200

Low

2.4

6.2

14.7

23.7

33.2

42.9

52.9

63.1

73.8

85.0

91.0

High

9.0

15.0

26.2

36.9

47.1

57.1

66.8

76.3

85.3

93.8

97.6

300

Low

2.8

6.8

15.6

24.9

34.4

44.2

54.2

64.5

75.0

86.0

91.9

High

8.1

14.0

25.0

35.5

45.8

55.8

65.6

75.1

84.4

93.2

97.2

500

Low

3.3

7.5

16.6

26.0

35.7

45.5

55.6

65.8

76.2

87.0

92.7

High

7.3

13.0

23.8

34.2

44.4

54.5

64.3

74.0

83.4

92.5

96.7

1000

Low

3.7

8.2

17.6

27.2

36.9

46.9

56.9

67.1

77.4

88.0

93.5

High

6.5

12.0

22.6

32.9

43.1

53.1

63.1

72.8

82.4

91.8

96.3


EXAMPLE:

It can be stated with 95% confidence that, at a sample size of 1000 and an observed value of 20%, the value of the parameter in the parent population will be in the interval of 17.6% to 22.6%.

To calculate sample error for parameter values not in the table, you can use the following calculator: