In the data, 0.20 ppm is an outlier and this can be rejected if there is a 95% confidence level.
When analyzing data an outlier is a value that is abnormal or too different from other data. In the case presented 0.20 can be tagged as an outlier because other values such as 0.11, 0.12, 0.13, and 0.14 are similar while 0.20 is outside this range.
The general rule is that if there is a 95% of confidence or higher you can reject an outlier, knowing the other data occurs 95% of the time, and therefore the outlier is improbable.
Based on this, you can reject an outlier if the confidence level is 95%.
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