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T-Mobile Wi-Fi 10:23 PM lowell.umassonline.net . A study was conducted to investigate the possible role of pesticides in the development of Parkinson's disease (PD). The study was conducted in the central valley of California, which has many farms and pesticides are used heavily Between 2001 and 2007, the investigators identified incident PD cases living in this area. They also selected a sample of the population living in this area who did not have PD. They used a variety of different data sources to determine whether or not each subject had been exposed to 3 common pesticides: ziram, maneb, and paraquat between 1974 and 1999. Of the 210 cases and 209 non-cases, they found that 46 PD cases and 18 of the non-cases had been exposed to all 3 pesticides combined. a. What kind of a study was this? b. What was the hypothesis being investigated? What was the c. What is a measure of association that you can calculate d. Calculate a measure of association. e. Write a few sentences to interpret and explain that measure null hypothesis? from these data? of association. 2. A study was conducted among children between the ages of 6 and 12, investigating the association between living on a farm and having asthma. The study was conducted at elementary schools in five rural areas in southern Germany, Switzerland, and Austria. A random sample of 9668 children was selected. Through questionnaires given to the parents, children were classified as either living full time on a farm, or not. They were also determined either to have asthma or not, based on standardized questions that have been previously validated in other studies. The study found that 1,450 of the children lived on farms. Of these farm children, 131 had asthma. Of the non-farm children, 986 had asthma. a. What kind of a study was this? b. What was the hypothesis being investigated? What was the null hypothesis? c. What is a measure of association that you can calculate from these data? d. Calculate a measure of association. e. Write a few sentences to interpret and explain that measure of association.

Answer 1

1.

a.

This is an observational study - a case-control study (case control study is a type of observational study) because there is no intervention by the researchers and they didn't introduce any control or treatment by themselves but just observed what happened to draw conclusions. And there are two groups in the study which are acting as treatment and control groups and so, it's called case control study.

b.

The hypothesis being investigated was whether there is an association between PD and pesticides.

Null Hypothesis: There is no association between PD and pesticides.

c.

The measure of association that can be calculated is "Relative risk".

d.

	Cases(PD)	Controls(No PD)	Total
Exposed to pesticides	46 (a)	18 (b)	64
Unexposed to pesticides	164 (c)	191 (d)	355
Total	210	209	419

​​​​Relative Risk, RR =[a/(a+b)]/[c/(c+d)] =(46/64)/(164/355) =0.71875/0.46197 =1.56

e.

The incidence of the disease in exposed group is 46/64 =0.72 =72%.

The incidence of the disease in unexposed group is 164/355 =0.46 =46%

The relative risk is greater than 1 (1.56 > 1), it means the risk for developing the disease(PD) for exposed group is higher than the unexposed group (72% > 46%).