Reiss et al. compared point-of-care and standard hospital
laboratory assays for monitoring patients receiving a single
anticoagulant or a regimen consisting of a combination of
anticoagulants. It is quite common when comparing two measuring
techniques, to use regression analysis in which one variable is used to
predict another. In the present study, the researchers obtained measures
of international normalized ratio (INR) by assay of capillary and venous
blood samples collected from 90 subjects taking warfarin. INR, used
especially when patients are receiving warfarin, measures the clotting
ability of the blood. Point-of-care testing for INR was conducted with
the CoaguChek assay product. Hospital testing was done with standard
hospital laboratory assays. The authors used the hospital assay INR
level to predict the CoaguChek INR level. The measurements are given in
the file EXR_C09_S03_04.csv.
Plot a scatter diagram and obtain the regression model and the \(p\). Plot it on the scatter
diagram.
Another variable of interest in the study by Reiss et
al. (exercise 1) was partial thromboplastin (aPTT), the standard test
used to monitor heparin anticoagulation. Use the data in the file
EXR_C09_S07_02.csv to examine the correlation between aPTT levels as
measured by the CoaguCheck point-of-care assay and standard laboratory
hospital assay in 90 subjects receiving heparin alone, heparin with
warfarin, and warfarin and exoenoxaparin.
A study by Scrogin et al. was designed to assess the effects of
concurrent manipulations of dietary NaCl and calcium on blood pressure
as well as blood pressure and catecholamine responses to stress.
Subjects were salt-sensitive, spontaneously hypertensive male rats.
Among the analyses performed by the investigators was a correlation
between baseline blood pressure and plasma epinephrine concentration
(E). The data in file REV_C09_16.csv on these two variables were
collected. Let \(\alpha = .01\).
Carry out the required analysis and test hypotheses at the indicated
significance levels. Compute the \(p\)
value for the linear model.
State all assumptions that are necessary to validate your analysis.
Describe the population(s) about which you think inferences based on
your analysis would be applicable.
The objective of a study by Peacock et al. was to investigate
whether spinal osteoarthritis is responsible for the fact that lumbar
spine \(bone\space mineral\space density\space
(BMD)\) is greater when measured in the anteroposterior plane
than when measured in the lateral plane. Lateral spine radiographs were
studied from women (age range 34–87 years) who attended a hospital
outpatient department for bone density measurement and underwent lumbar
spine radiography. Among the data collected (file REV_C09_41.csv) were
the measurements on anteroposterior (A) and lateral (L) \(BMD (g/cm^2)\).