Inorganic phosphorous is a naturally occurring element in all plants and animals
ID: 3261615 • Letter: I
Question
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. The Hill of Tara is a very important archaeological site in Ireland. It is by legend the seat of Ireland's ancient high kings†. Independent random samples from two regions in Tara gave the following phosphorous measurements (ppm). Assume the population distributions of phosphorous are mound-shaped and symmetric for these two regions.
(a) Use a calculator with mean and standard deviation keys to calculate x1, s1, x2, and s2. (Round your answers to one decimal place.)
(b) Let 1 be the population mean for x1 and let 2 be the population mean for x2. Find an 80% confidence interval for 1 2. (Round your answers to one decimal place.)
Explanation / Answer
a]
x1 = 747.5 ppm
s1 = 170.4ppm
x2 = 738.9 ppm
s2 = 212.1 ppm
b]
80% confidence interval for 1 2
Assume equal variances of Region I and II
80% CI for difference: (-89.6, 106.8)
Both use Pooled StDev = 195.5776
and when assume variance are not same of Region I and II
80% CI for difference: (-86.7, 103.8)