Researchers in toxicology study
Question # 00618342
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Updated on: 11/15/2017 08:39 AM Due on: 11/15/2017
(60 points) Researchers in toxicology study were interested in evaluating the effects of
air pollution on vasoconstriction of small pulmonary arteries in rats. Also, they wanted
to know if these health effects differed according to whether the rats had preexisting
pulmonary disease. Thus, chronic bronchitis was induced in some of the rats by exposing
them to 802 for 6 weeks prior to pollution exposure. All rats were randomized to one
of four groups:
air pollution on vasoconstriction of small pulmonary arteries in rats. Also, they wanted
to know if these health effects differed according to whether the rats had preexisting
pulmonary disease. Thus, chronic bronchitis was induced in some of the rats by exposing
them to 802 for 6 weeks prior to pollution exposure. All rats were randomized to one
of four groups:
0 ?ltered air, not exposed to 802
o concentrated air particles (CAPS), not exposed to 802
o ?ltered air, exposed to 802
o concentrated air particles (CAPS), not exposed to 802
o ?ltered air, exposed to 802
o concentrated air particles (CAPS), exposed to 802 and the amount of pulmonary in?ammation, as measured by neutrophil numerical den-
sity (Nn) in each animal was measured after three successive days of air pollution ex-
posure. A large value of Nn denotes pulmonary in?ammation. The data are contained
in the ?le pollution. sas7bdat, and variables CAPS, 802 and Nn are named as caps,
$02, and 1m therein.
sity (Nn) in each animal was measured after three successive days of air pollution ex-
posure. A large value of Nn denotes pulmonary in?ammation. The data are contained
in the ?le pollution. sas7bdat, and variables CAPS, 802 and Nn are named as caps,
$02, and 1m therein.
(a) (15 points) Consider the main effect model and the interaction model (which con-
tains both main effects and interactions) that simultaneously assess two categorical
factors (802 and CAPS). Write down these two regression models, making sure to
explicitly de?ne all independent variables. Write out the interpretation of each
regression coefficient Speci?ed in each of these two models.
tains both main effects and interactions) that simultaneously assess two categorical
factors (802 and CAPS). Write down these two regression models, making sure to
explicitly de?ne all independent variables. Write out the interpretation of each
regression coefficient Speci?ed in each of these two models.
(b) (10 points) Consider a test of whether there is a difference in the health effects of
air pollution inhalation for healthy animals and that for chronic bronchitic animals
(i.e. those who received 802) under the interaction model. What is the null hypothesis correSponding to this test, in terms of the regression coef?cients under
the interaction model?
air pollution inhalation for healthy animals and that for chronic bronchitic animals
(i.e. those who received 802) under the interaction model. What is the null hypothesis correSponding to this test, in terms of the regression coef?cients under
the interaction model?
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Solution: Researchers in toxicology study