1. Assignment and Discussion
For this module, you will need to obtain more data. As you did in Module 7, visit the United States Environmental Protection Agency's download daily data page athttps://www.epa.gov/airdata/ad_data_daily.html new window. Collect data with the same parameters as you did before but for one thing; this time collect data for 2015. When you download this data, save it to a new Excel file. Look in your data set for the AQS_Parameter_Code column. If you have two different measuring methods, please remove the data for one of them. Having done this, copy this data into a new tab in the worksheet you were using for Module 7. Give this new tab a descriptive name.
For this new data, use Excel's COUNTIF function to find the number of days with a PM2.5 AQI value over 50. Use this to find the proportion of days for which the air quality was not good in your sample. You will need to know the number of successes, the sample size, and the proportion of successes for to continue.
Create a new tab in your worksheet and label. Perform a four-step hypothesis test (hypothesize, prepare, compute to compare, and interpret) to test whether the proportion of days which do not have "Good" air quality has changed. Insert any work done using StatCrunch into your Mod 8 tab. Tech Tips for using StatCrunch can be found at the end of Chapter 8. Include clear verbal explanation for each of the steps
2. Assignment and Discussion
National Ambient Air Quality Standards (NAAQS) can be found at the EPA's website. Link opens in a new windowhttps://www3.epa.gov/ttn/naaqs/criteria.html. Over the past 50 years the standard annual mean for fine particulate matter PM2.5 has been significantly tightened, starting out at 75 µg/m3 of air in 1971 and now only 12 µg/m3 of air (as of 2012 standards).
For this discussion you will be using your 2015 data. Create a new tab in your worksheet and name. Note the two conditions for a valid confidence interval are met. Use StatCrunch to find a 90% confidence interval for the column Daily Mean PM2.5 Concentration.
Is the 12 µg/m3 of air standard limit contained in your confidence interval? With standards getting stricter over time, it is possible that even if it the current standard is not contained in the confidence interval a future stricter standard might be. What concerns might you have if this were contained in your confidence interval? What can you interpret from this?
The textbook noted that confidence intervals may be reported in two different ways. Please give your results in both formats. Which format do you find to be more useful or clearer?
Now, utilize Excel's COUNTIF function to find how many days in your data set had a Daily Mean PM2.5 Concentration over 12 µg/m3. Did your area have any days over the standard annual mean for fine particulate matter, and if so how many? Note that the 12 µg/m3 is an annual mean so that over the course of the year the AVERAGE for any given area should be under that value. As an average, one would expect some days to be higher and some days to be lower concentrations, but the overall average for the year should be below this value to meet the EPA's standards.