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Contamination of New Jersey Wells

Methyl t-butyl ether (MTBE) is an organic water contaminant that often results from gasoline spills. The level of MTBE (in parts per billion) was measured for a sample of 12 well sites located near a gasoline service station in New Jersey (Environmental Science & Technology, Jan. 2005). The data are listed in the accompanying table and saved in the NJGAS file.

150 367 38 12 11 134
12 251 63 8 13 107

Calculate and interpret a 99% confidence interval for the mean.

Here is the answer that I came up with. Can you check it for accuracy and explain the interpretation of this problem.

Confidence interval - mean

99% confidence level
97.2 mean
10.67 std. dev.
12 n
2.576 z
7.934 half-width
105.134 upper confidence limit
89.266 lower confidence limit

Solution Preview

MTBE Level
150
367
38
12
11
134
12
251
63
8
13
107

Mean 97.16666667
Standard Deviation ...

Solution Summary

Contamination of New Jersey Wells is examined. The environmental science and technology is analyzed.

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