In: Statistics and Probability
Inorganic phosphorous is a naturally occurring element in all
plants and animals, with concentrations increasing progressively...
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.
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. (Round your
answers to one decimal place.)
(b) Let μ1 be the population mean for
x1 and let μ2 be the
population mean for x2. Find a 90% confidence
interval for μ1 − μ2.
(Round your answers to one decimal place.)
Region I: x1;
n1 = 15 |
855 |
1550 |
1230 |
875 |
1080 |
2330 |
1850 |
1860 |
2340 |
1080 |
910 |
1130 |
1450 |
1260 |
1010 |
Region II: x2;
n2 = 14 |
540 |
810 |
790 |
1230 |
1770 |
960 |
1650 |
860 |
890 |
640 |
1180 |
1160 |
1050 |
1020 |
(c) Use a calculator with mean and standard deviation keys to
verify that x1, s1,
x2, and s2. (Round your
answers to one decimal place.)
(d) Let μ1 be the population mean for
x1 and let μ2 be the
population mean for x2. Find a 90% confidence
interval for μ1 − μ2.
(Round your answers to one decimal place.)