Analysis of uncertainty - spreadsheet model
It is useful to summarise the uncertainty analysis in a spreadsheet.
Spreadsheet model showing the ‘uncertainty analysis’
|
Source of uncertainty |
Value ± |
Probability distribution |
Divisor |
Standard Uncertainty |
|
Calibration uncertainty |
5.0 mm |
Normal |
2 |
2.5 mm |
|
Resolution (size of divisions) |
0.5 mm* |
Rectangular |
√3 |
0.3 mm |
|
String not lying perfectly straight |
10.0 mm* |
Rectantular |
√3 |
5.8 mm |
|
Standard uncertainty of mean of 10 repeated readings |
0.7 mm |
Normal |
1 |
0.7 mm |
|
Combined standard uncertainty |
Assumed normal |
6.4 mm |
||
|
Expanded uncertainty |
Assumed normal (k=2) |
12.8 mm |
* Here the (±) half-width (a) divided by square root of 3 is used.
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