Ten samples of coal from a Northern Appalachian source had an average mercury content of 0.242 ppm with a standard deviation of 0.031 ppm. 14. Find the lower limit of the 95% confidence interval for the mean mercury content of coal from this source. Round your answer to three decimal places

The lower limit of the 95% confidence interval for the mean mercury content of coal from this source is 0.185 ppm.

Step-by-step explanation:

We have the standard deviation of the sample, so we use the t-distribution to solve this question.

The first step to solve this problem is finding how many degrees of freedom, we have. This is the sample size subtracted by 1. So

df = 10 - 1 = 9

Now, we have to find a value of T, which is found looking at the t table, with 9 degrees of freedom(y-axis) and a confidence level of 0.95(). So we have T = 1.833

The margin of error is:

M = T*s = 1.833*0.031 = 0.057

In which s is the standard deviation of the sample.

The lower end of the interval is the sample mean subtracted by M. So it is 0.242 - 0.057 = 0.185

The lower limit of the 95% confidence interval for the mean mercury content of coal from this source is 0.185 ppm.

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step-by-step explanation:

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