The water department checks the city water supply on a regular basis for contaminants such as xylenes. The water department takes 200 samples and estimates that the concentration of xylenes in your drinking water is 3.5 ppb, with a standard deviation of 0.2 ppb. Assuming the samples were random and unbiased, how much confidence can you have in this data

A. 68% confident the average concentration of PCBs in the water supply is between 3.3 ppb and 3.7 ppb.

B. 95% confident the average concentration of PCBs in the water supply is between 3.3 ppb and 3.7 ppb.

Question

The water department checks the city water supply on a regular basis for contaminants such as xylenes. The water department takes 200 samples and estimates that the concentration of xylenes in your drinking water is 3.5 ppb, with a standard deviation of 0.2 ppb. Assuming the samples were random and unbiased, how much confidence can you have in this data

A. 68% confident the average concentration of PCBs in the water supply is between 3.3 ppb and 3.7 ppb.

B. 95% confident the average concentration of PCBs in the water supply is between 3.3 ppb and 3.7 ppb.

anonymous · Answer

C. 99.7% confident the average concentration of PCBs in the water supply is between 2.7 ppb and 4.3 ppb.

D. 97% confident the average concentration of PCBs in the water supply is between 3.1 ppb and 3.9 ppb.

anonymous · Answer

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anonymous · Answer

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