Acid rain - According to the US Environmental Protection Agency (EPA), "normal, clean rain has a pH value of between 5.0

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Acid Rain According To The Us Environmental Protection Agency Epa Normal Clean Rain Has A Ph Value Of Between 5 0 1 (92.18 KiB) Viewed 26 times

Acid rain - According to the US Environmental Protection Agency (EPA), "normal, clean rain has a pH value of between 5.0 and 5.5, which is slightly acidic. However, when rain combines with sulfur dioxide or nitrogen oxide--produced from power plants and automobiles--the rain becomes much more acidic. Typical acid rain has a pH value of 4.0." Between 1992 and 2015, samples of rainwater collected at the Walker Branch Watershed in Tennessee had an average pH of 4.45. A histogram of these observations is shown. Walker Branch Watershed Rainwater Frequency ន្ត - 3.5 40 55 60 4.5 5.0 pH of rainwater sample A researcher at the Walker Branch Watershed is interested in more recent measurements of the pH of rainwater. They obtain a random sample of 15 rainwater samples from this year and calculate a mean pH measurement of * = 4.409 with a standard deviation of 8 – 0.3376. Round all calculated values to 4 decimal places as appropriate. 1. Calculate a 95% confidence interval for the mean pH of rainwater for this year.

2. If the researcher wants to estimate the mean pH of rainwater at 95% confidence with a margin of error of no more than 0.09, how many rainwater samples should they measure? Use a t' value rounded to three decimal places and the sample information above to calculate your answer. Your answer should be an integer value. T2 the histogram shown above, they also construct the Normal Q-Q plot of the 3. The researcher wants to check to make sure using a t-distribution procedure is appropriate for the situation. In addition sample data from this year: Normal Q-Q Plot Sample Quantiles + 01 DE a Theoretical Quantiles Is using a t-distribution procedure appropriate for the situation? ? because (select all that apply) O A. A sample size of 15 is too small.

B. The Q-Q plot does not indicate that the sample data is normally distributed. C. The researcher chose a random sample of rainwater samples which can be assumed to be independent. D. It is safe to assume the population data is approximately normal because the historical data appears to be normally distributed. 4. Another researcher who works for a National Park in a neighboring state doing similar work collects a sample of 28 recent rainwater pH measurements and constructs a 95% interval of (4.334, 4.596). Select the statement(s) below that is/are appropriate interpretation(s) of this confidence interval procedure. A. Approximately 95% of the rainwater samples will have mean pH values between 4.334 and 4.596. B. Approximately 95% of the confidence intervals constructed using this process will contain the true mean pH of rainwater this year. C. We can be 95% confident that the true mean pH of rainwater this year is between 4.334 and 4.596. D. There is a 95% chance that the true mean pH of rainwater this year is between 4.334 and 4.596.