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MCS,PHD
Argosy University/ Phoniex University/
Nov-2005 - Oct-2011
Professor
Phoniex University
Oct-2001 - Nov-2016
5.11.Â
A physical anthropologist performed a mineral analysis of nine ancient Peru vian hairs.  The results for the chromium ( x1 ) and strontium ( x2) levels, in parts per million (ppm), were as follows:
Â
|
x1(Cr) |
.48 |
40.53 |
2.19 |
 |
.74 |
.66 |
.93 |
.37 |
.22 |
|
x2(Cr) |
12.57 |
73.68 |
11 .13 |
20 .03 |
20.29 |
.78 |
4.64 |
.43 |
1.08 |
Source: Benfer and others, "Mineral Analysis of Ancient Peruvian Hair,"
American Journal ofPhysical Anthropo logy, 48, no. 3 (1978), 277-282.
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It is known that low levels (less than or equal to .100 ppm) of chromium sug gest the presence of diabetes. while strontium is an indication of animal pro tein intake.
(a) Construct and plot a 90% joint confidence ellipse for the population mean vector IL' == [,u1 , ,u2], assuming that these nine Peruvian hairs represent a random sample from individuals belonging to a particular ancient Peruvian
culture.
(b) Obtain the individual simultaneous 90% confidence intervals for ,u1 and ,u2 by "projecting" the ellipse constructed in Part a on each coordinate axis. (Alternatively, we could use Result 5.3 . ) Does it appear as if this Peruvian culture has a mean strontium level of 10? That is, are any of the points  (,u1
arbitrary, 10) in the confidence regions? Is [.30, 10] ' a plausible value  for
IL? Discuss.
(c) Do these data appear to be bivariate normal? Discuss their status with refÂ
erence to Q-Q plots and a scatter diagram. If the data are not bivariate normal, what implications does this have for the results in Parts a and  b?
(d) Repeat the analysis with the obvious "outlying" observation removed.  Do
the inferences change?  Comment.
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