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Smoking and heart attacks A Reuters story (April 2,2003) reported that "The number of heart attack victims fell by almost \(60 \%\) at one hospital six months after a smoke-free ordinance went into effect in the area (Helena, Montana), a study showed, reinforcing concerns about second-hand smoke." The number of hospital admissions for heart attack dropped from just under seven per month to four a month during the six months after the smoking ban. a. Did this story describe an experiment or an observational study? b. In the context of this study, describe how you could explain to someone who has never studied statistics that association does not imply causation. For instance, give a potential reason that could explain this association.

Short Answer

Expert verified
a. Observational study. b. Association does not imply causation; other factors, like public health awareness, may explain the reduction in heart attacks.

Step by step solution

01

Understand the Type of Study

The story talks about observing changes in heart attack rates after implementing a smoke-free ordinance. There was no random allocation of subjects to smoking or non-smoking environments. Thus, the researchers observed natural conditions rather than imposing any controlled experimental conditions. Therefore, this was an observational study.
02

Define Association and Causation

Association means a relationship between two variables, indicating they occur together more frequently than by chance, whereas causation suggests that one variable directly influences the other. This distinction is critical in statistical studies.
03

Explain Association Without Causation

While the study found a lower number of heart attack admissions after the smoking ban, this only implies an association. Other factors might contribute to the reduction, such as improved overall public health or seasonal variations that coincidentally align with the timing of the ban. Without controlled experiments, it’s not possible to claim the smoke-free ordinance directly caused the reduction.
04

Suggest Alternative Explanations

To illustrate why association does not imply causation, one could suggest that increased public health awareness campaigns or changes in local diet and exercise habits could also explain the drop in heart attacks. Hence, attributing the drop solely to the smoking ban without other evidence would be misleading.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Association vs Causation
When we talk about association and causation, we're dealing with two different concepts. Association is simply when two things occur together more often than you would expect by chance. It's like finding that whenever you eat ice cream, you tend to be in a park, but that doesn't mean ice cream causes you to go to the park.
On the other hand, causation means one thing directly influences another. For example, pushing a button on a remote causing the TV to turn on. This is a clear cause-and-effect relationship.
In statistical studies, it's important not to jump from association to causation. Just because two events appear linked doesn't mean one caused the other. There may be other underlying factors at play that we need to consider. For example, the study on heart attacks may reveal an association between smoking bans and fewer heart attacks, but without strict controls, we can't conclude the ban caused this change.
Smoking Ban Effects
The smoking ban in Helena, Montana, is a great example to discuss potential benefits of such policies. After the ban, heart attack admissions at a local hospital reportedly dropped by almost 60% in six months.
This sounds promising, but we need to be cautious in interpreting these numbers as directly caused by the smoking ban. There are numerous reasons why heart attacks might decrease. For instance, there might have been other simultaneous health initiatives, like increased public health campaigns or better lifestyle choices made by people in the community.
It's tempting to attribute the drop in heart attacks directly to the smoking ban, but we must consider all the possible factors and recognize this result as an interesting association rather than conclusive evidence of causation.
Statistical Studies
Statistical studies like the one described in Helena help us understand complex issues, but they come with limitations, especially when they are observational studies rather than controlled experiments.
Observational studies observe outcomes without manipulating the environment or subjects. While they can reveal associations, they cannot prove causation. This is because numerous variables may be in play, and it's challenging to isolate the impact of one specific factor like a smoking ban.
For more definitive evidence, a randomized controlled trial would be ideal, where participants are assigned randomly to either experience the smoking ban or not, and all other factors are held constant. This type of study would do a better job at revealing cause-and-effect relationships, giving stronger grounds to make causal claims about the effects of smoking bans.
Nonetheless, observational studies remain valuable as they often serve as the first step to understanding associations in real-world settings and can guide further, more rigorous research.

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Most popular questions from this chapter

Bias due to perceived race A political scientist at the University of Chicago studied the effect of the race of the interviewer. \(^{8}\) Following a phone interview, respondents were asked whether they thought the interviewer was black or white (all were actually black). Perceiving a white interviewer resulted in more conservative opinions. For example, \(14 \%\) agreed that "American society is fair to everyone" when they thought the interviewer was black, but \(31 \%\) agreed to this statement when posed by an interviewer that the respondent thought was white. Which type of bias does this illustrate: Sampling bias, nonresponse bias, or response bias? Explain.

Sampling your fellow students You are assigned to direct a study on your campus to discover factors that are associated with strong academic performance. You decide to identify 20 students who have perfect GPAs of 4.0 , and then measure explanatory variables for them that you think may be important, such as high school GPA and average amount of time spent studying per day. a. Explain what is wrong with this study design. b. Describe a study design that would provide more useful information.

Aspirin prevents heart attacks? During the 1980 s approx imately 22,000 physicians over the age of 40 agreed to participate in a long-term study called the Physicians' Health Study. One question investigated was whether aspirin help to lower the rate of heart attacks. The physicians were randomly assigned to take aspirin or take placebo. a. Identify the response variable and the explanatory variable. b. Explain why this is an experiment, and identify the treatments. c. There are other explanatory variables, such as the amount of exercise a physician got, that we would expect to be associated with the response variable. Explain how such a variable is dealt with by the randomized nature of the experiment.

Capture-recapture Biologists and naturalists often use sampling to estimate sizes of populations, such as deer or fish, for which a census is impossible. Capture-recapture is one method for doing this. A biologist wants to count the deer population in a certain region. She captures 50 deer, tags each, and then releases them. Several weeks later, she captures 125 deer and finds that 12 of them were tagged. Let \(N=\) population size, \(M=\) size of first sample, \(n=\) size of second sample, \(R=\) number tagged in second sample. The table shows how results can be summarized. a. Identify the values of \(M, n,\) and \(R\) for the biologist's experiment. b. One way to estimate \(N\) lets the sample proportion of tagged deer equal the population proportion of tagged deer. Explain why this means that $$ \frac{R}{n}=\frac{M}{N} $$ and hence that the estimated population size is \(N=(M \times n) / R\) c. Estimate the number of deer in the deer population using the numbers given. d. The U.S. Census Bureau uses capture-recapture to make adjustments to the census by estimating the undercount. The capture phase is the census itself (persons are "tagged" by having returned their census form and being recorded as counted) and the recapture phase (the second sample) is the postenumerative survey (PES) conducted after the census. Label the table in terms of the census application.

Nursing homes You plan to sample residents of registered nursing homes in your county. You obtain a list of all 97 nursing homes in the county, which you number from 01 to 97 . Using random numbers, you choose five of the nursing homes. You obtain lists of residents from those five homes and interview all the residents in each home. a. Are the nursing homes clusters or strata? b. Explain why the sample chosen is not a simple random sample of the population of interest to you.

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