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Adjusting
measurements or samples
Degrees of
freedom
68.27
1
1.84
2
1.32
3
1.2
4
1.14
5
1.11
6
1.09
7
1.08
8
1.07
9
1.06
10
1.05
20
1.03
50
1.01
100
1.005
1
For our example with the effective degrees of freedom (V
a coverage factor of 2.57 expands
(compared to 1.96 for an infinite set of measurements/samples).
©Fluke Calibration 2011
k
for a smaller set of
Fraction p in percent
90
95
95.45
6.31
12.71
13.97
2.92
4.3
4.53
2.35
3.18
3.31
2.13
2.78
2.87
2.02
2.57
2.65
1.94
2.45
2.52
1.89
2.36
2.43
1.86
2.31
2.37
1.83
2.26
2.32
1.81
2.23
2.28
1.72
2.09
2.13
1.68
2.01
2.05
1.66
1.984
2.025
1.645
1.96
2
Basics Of Measurement Uncertainty for DMM Calibration
• Adjusting
99
99.73
63.66
235.8
9.92
19.21
• A coverage factor adjustment
5.84
9.22
4.6
6.62
is needed because our data
4.03
5.51
3.71
4.9
set had a fewer number of
3.5
4.53
values, rather than a larger set
3.36
4.28
3.25
4.09
(such as 20, 50, or 100)
3.17
3.96
• The table lists the proper
2.85
3.42
coverage factor for populations
with smaller degrees of
2.68
3.16
2.626
3.077
freedom
2.576
3
u
to a value with 95% confidence
c
k
is done using the:
students' t distribution table
) of 5.2,
eff
54
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