ENVM 510 Environmental Health and Epidemiology Fall 2016 Week 5 Graded Assignmen
ID: 802542 • Letter: E
Question
ENVM 510
Environmental Health and Epidemiology
Fall 2016
Week 5
Graded Assignment
Instructions:
The use of statistics in epidemiology to helps determine differences in risk due to exposures and allows for the evaluation of associations with respect to validity in order to strengthen study conclusions. Imagine that you are an epidemiologist investigating the development of leukemia associated with occupational exposures to benzene. Employment records identify a total of 9,024 individuals who have worked in a facility where benzene is present. Of the 9,024 individuals, you are able to locate 3,249 individuals. Of those persons located, 487 have leukemia.
Your investigative team also decides to conduct an occupational surveillance program at a facility to identify those who are subjected to excessive benzene exposures. You screen a total of 1,832 workers using a new diagnostic test, and 214 workers with excessive benzene exposure test positive. A negative test finding was observed in 29 workers who had excessive exposure to benzene, and 90 workers without excessive benzene exposure tested positive.
1. Identify potential sources of bias in this study.
2. Describe how these potential sources of bias could be addressed in future studies.
3. Based on the results of the screening test, construct a 2 x 2 table and calculate the following measures:
Sensitivity
Specificity
Prevalence of excessive benzene exposure
Positive predictive value
Negative predictive value
Accuracy
4. Based on the results of the screening program, what conclusions would you draw regarding the new diagnostic test?
Please make sure that you answer each part of the question and that you do so using complete sentences, proper spelling and grammar, etc. Make sure your answers are thorough, yet concise and that you support your responses with at least two (2) appropriately cited references. Wikipedia is not an acceptable reference. Submission Instructions:Assignments must be submitted in Word file as Lastname_ENVM510_M5GradedAssign by 11:55pm EST on Friday, September 3 2016
Explanation / Answer
Benzene is a highly volatile compound and its effect is mainly through inhalation. The high levels of benzene is found mainly in indoor airs, industrial processes, inside vehicles, food and water.
The possible sources of bias could be due to human induced errors while measuring the benjene levels in the people producing erronerous results . It could due to that the instrument is not working properly.
These bias can be removed by the use of different persons for measuring the readings and then taking their average. Also the skilled workers should be employed to remove this error considerably. Also the upgradation and calibration of the instruments is required.
Prevalance= diseased/ total *100
=214+29/1832*100=13%
Senstivity=True postive/ True positive+ false negative
=214/214+29=214/243=88%
Specificity=True negative/ True negative+false positive
=29/29+90
=24%
Positive predictive value
=True positive/ total positive
=214/214+90=70
Negative predictive value
=True negative divided by(false negative + true negative)
=90/90+90+29=75.6
=76
References:
https://onlinecourses.science.psu.edu/stat507/node/71
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