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# Consider each of the following scenarios and explain whether

Consider each of the following scenarios and explain whether the variable in question is a confounder: (Remember to answer "yes" or "no" and then explain why)

1. A study of the relationship between exercise and heart attacks that is conducted among women who do not smoke. Explain whether gender is a confounder. (0.5 point)
2. A case-control study of the relationship between liver cirrhosis and alcohol use. In this study, smoking is associated with drinking alcohol and is a risk factor for liver cirrhosis among both non-alcoholics and alcoholics. Explain whether smoking is a confounder. (0.5 point)

Interpret the results of the following studies (This is mostly from Chapter 12. Please answer each question concisely. I think one single paragraph is sufficient. Don't make your answer too lengthy.)

1. An odds ratio of 1.2 (95% confidence interval: 0.8-1.5) is found for the association of low socioeconomic status and occurrence of obesity. (0.5 point)
2. A relative risk of 3.0 is reported for the association between consumption of red meat and the occurrence of colon cancer. The p-value of the association is 0.15. (0.5 point)
3. An odds ratio of 7 (95% confidence interval: 3.0 – 11.4) is found for the association of smoking and lung cancer. (0.5 point)

The relationship between cigarette smoking and lung cancer was conducted in a case-control study with 700 cases and 425 controls. Using the results below, calculate the crude odds ratio and explain what the ratio means: (Remember to calculate "odds ratio" and explain the results - is heavy smoking increase the risk for lung cancer or not?)
Heavy Smoking—Cases: 450; Controls: 200
Not Heavy Smoking—Cases: 250; Controls: 225
(1.5 points for the whole calculation and explanation. You NEED to make a 2 by 2 table to receive a full point)
(The following is the beginning of another set of question - about alcohol, heart disease, and smoking as a confounder)
A case-control study looked at the association of alcohol use with the occurrence of coronary heart disease (CHD). There were 300 participants in the study (150 cases and 150 controls). Of the cases, 90 participants drank alcohol; of the controls, 60 participants drank alcohol.

Design the appropriate 2x2 table, calculate and interpret the appropriate measure of association. (Remember, you need to make a 2x2 table for this set of question too; In addition, answer the question "what is the appropriate measure of association? relative risk or odds ratio?" then do the calculation; then interpret the results of your calculation. ) (1 point for this segment)

You suspect that the association between alcohol use and CHD might be confounded by smoking. You collect the following data:

Smokers Non-Smokers
CHD No CHD CHD No CHD
Alcohol Use 80 40 10 20
No Alcohol Use 20 10 40 80

Calculate the appropriate measure of association between alcohol use and CHD in both smokers and non-smokers. Discuss whether smoking was a confounder of the association. What is the relationship of alcohol use to CHD after controlling for confounding?
(Here, two 2x2 tables are already drawn for you. Thus, what you need to do here is "calculate the measure of association; then, discuss if smoking was a confounder.) (1 point for this segment)

(The following is the beginning of another set of question - about drivers' education, ca accidents, and gender as an effect modifier)
A study was conducted in young adults to look at the association between taking a driver's education class and the risk of being in an automobile accident. 450 participants were included in the study, 150 cases who had been in an accident and 300 controls who had not. Of the 150 cases, 70 reported having taken a driver's education class. Of the 300 controls, 170 reported having taken a driver's education class.

Calculate and interpret the appropriate measure of association between driver's education and accidents.

(Again, you need to make a 2x2 table for this set of question too; In addition, answer the question "what is the appropriate measure of association? relative risk or odds ratio?" then do the calculation; then interpret the results of your calculation. ) (1 point for this segment)

The question arose as to whether gender might be an effect modifier of this association. When gender was assessed, the data looked like the following:
Women Men
Accident No Accident Accident No Accident
Driver's Ed 10 50 60 120
No Driver's Ed 40 50 40 80

Perform the appropriate calculations to test for effect modification. Interpret your results.
(Here again, two 2x2 tables are already drawn for you. Here what you need to do is "calculate the measure of association; then, discuss if gender might be an effect modifier for the association between drivers' education and car accidents. Then discuss why.) (1 point for this segment)

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Customer: replied 3 years ago.

For number two, not sure why smoking would not be a confounder. Doesn't It affect both variables, liver cirrhosis and alcohol use?

Yes, you'd be right there. Smoking would be more prevalent in alcoholic group, thus higher incidence of liver cirrhosis, confounding the result.
Thanks for pointing that out!
Customer: replied 3 years ago.

Overall ok. I just needed a second opinion on a few because I struggle with this subject.

Sure, no problem!