Exhaust is bad for your heart. A CNET News Article reported that the artery wall

Question

Exhaust is bad for your heart. A CNET News Article reported that the artery walls of people living within 100 meters of a highway thicken more than twice as fast as the average person's. Researchers used ultrasound to measure the carotid artery wall thickness of 1483 people living within 100 meters of a highway increased by 5.5 micrometers (roughly 1/20th the thickness of a uman hair) each year during the three-year study, which is more than twice the progression observed in participants who did not live within this distance of a highway.

(a) What are the explanatory and response variables?

(b) Explain carefully why this study is not an experiment.

(c) Explain why confounding prevents us from concluding that living near a highway is bad for your heart becasue it causes increased thickness in the carotid artery wall.

Explanation / Answer

(a) (i) The increased thinckness of the carotid artery wall is the response variable as it is is the specific parameter that we measured in our above study.

(ii) The proximity or the distance of residences of the people observed is an explanatory variable as it is the feature that we believe can impact the response variable.

(b) This study is not an experiment becuse here researchers have simply collected data on carotid wall thicknesses and distance from highways based on what is seen and infered based on the data collected, instead of applying the distance from highway condition on an homogenous group and then splitting it into a test and control groups respectively to more accuratly evaluate the impact of the distance from highway on the thickness of carotid artery.

(c) Confounding is the important variable which when missed can lead us to make an incorrect relation of cause and effect. In this case, age of the participants could be the critical missing / confounding variable (known fact: the risk of thickness in the carotid artery wall increases with age) which prevents us from concluding that living near a highway is bad for your heart becasue it causes increased thickness in the carotid artery wall.

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