Answer:
1. B
2. A
3. A
4. A
Step-by-step explanation:
Hello!
The study claimed that subjects who suffer depression are more likely to have a heart attack than those who are not depressed.
1551 persons were interviewed as part of the experiment and classified according to their answers in two groups "suffered depression" and "didn't suffer depression"
Afterward, the researchers looked up the medical history of all 1551 subjects and recorded how many of them had heard issues.
1.
An observational study is one where the researcher only determines the variables he wants to study without controlling or influencing any factor of the population of interest. Because there is no interference from the researchers, there is a high risk that confounding factors may affect the conclusions of it. These studies are usually precursors to experimental tests, it allows the researcher to have an idea of the association between the two variables but you cannot establish causal relationships from them.
This is an example of an observational study, the researcher merely recorded the variables of interest without interfering with any aspects that may influence them. (For example diet or exercise habits of the subjects)
2. and 3.
The objective of the study is to determine if "depression" causes "disposition to heart attacks"
The explanatory variable is "depression status of the subject" since it is what is suspected to influence over the heart condition of said subject and "heart attack status" is the response variable.
4.
Of the 1551 subjects originally studied, 444 were classified as depressed, of these 27 had heard attacks. You can calculate the "proportion of subjects that suffered depression and had heart attacks" as:
p': 27/444= 0.06 ⇒ 6%
Since this value was obtained from the sample, it is an estimation of the population parameter, also called statistic.
I hope it helps!
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