Assignment:
To test the quality of work of a commercial laboratory, 15 replicate analyses of a purified benzoic acid (68.8% C, 4.953%H) sample were requested. The absolute standard deviation of the method is s=4ppt for carbon and s=6ppt for hydrogen. The means of the reported results are 68.5% C and 4.882% H. At the 95% confidence level, is there any indication of systematic error in either analysis?
for 95% confidence the degrees of freedom are as follows:
Number of observatoins 95% Confidence
3 0.970
4 0.829
5 0.710
6 0.625
7 0.568
8 0.526
Degrees of Freedom Factor for Confidence Interval95%
1 12.7
2 4.30
3 3.18
4 2.78
5 2.57
6 2.45
7 2.36
8 2.31
9 2.26
10 2.23
11 2.20
12 2.18
13 2.16
14 2.14
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