"Inorganic phosphorous is a naturally occurring element in all plants and animals", with concentrations increasing progressively up the food chain (fruit < vegetables < cereals < nuts < corpse). Geochemical surveys take soil samples to determine phosphorous content (in ppm, parts per million). A high phosphorous content may or may not indicate an ancient burial site, food storage site, or even a garbage dump. Independent random samples from two regions gave the following phosphorous measurements (in ppm). Assume the distribution of phosphorous is mound-shaped and symmetric for these two regions.

Region I: x1; n1 = 12
540 810 790 790 340 800
890 860 820 640 970 720

Region II: x2; n2 = 16
750 870 700 810 965 350 895 850
635 955 710 890 520 650 280 993

a. Use a calculator with mean and standard deviation keys to calculate x1, s1, x2, and s2. (Use 1 decimal place.)
b. Let µ1 be the population mean for x1 and let µ2 be the population mean for x2. Find a 95% confidence interval for µ1 - µ2.