Arsenic is frequently found both in the natural environment and in food. A study
ID: 3222971 • Letter: A
Question
Arsenic is frequently found both in the natural environment and in food. A study of the relationship between arsenic in drinking water and deaths from lung cancer measured arsenic levels in drinking water in 138 villages in Taiwan and examined death certificates to identify lung cancer deaths. The study summary says that "arsenic levels above 0.64 mg/l were associated with a significant increase in the mortality of lung cancer in both genders, but no significant effect was observed at lower levels."
Explain why this is an observational study rather than an experiment.
It is an observational study because a variable has been influenced to study the outcome.
It is an observational study because there is no need to eliminate a lurking variable in this study.
It is an observational study because the researchers simply observed the existing arsnic levels. They did not alter them.
It is an observational study because it only measures a variable of interest.
The word "significant" in the conclusion has a statistical meaning, different from its everyday meaning. Restate the study conclusion without using the word "significant" in a way that is clear to readers who know no statistics.
Arsenic plays an expressive role in increased lung cancer mortality.
The increased lung cancer mortality rate in high arsnic regions is greater than would be likely to occur by chance if arsenic had no effect on lung cancer.
Lung cancer mortality would not be expected to increase if drinking water would be free of arsenic.
Arsenic is a meaningful cause for the increased lung cancer mortality.
Explanation / Answer
ANSWER :-
1)
It is an observational study because the researchers simply observed the existing arsenic levels. They did not alter them .
2)
The increased lung cancer mortality rate in high arsenic region is greater than would be likely to occur by chance if arsenic had no effect on lung cancer.
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