Part 2

You've done a case control study of the relationship of benzene exposure in factory workers and bladder cancer, and come up with the following 2x2 table:

	Exposed	Not exposed
Bladder cancer	20	10	30
No cancer	20	30	50
	40	40	80

Calculate the Odds Ratio. (10 points)

OR =

But exposure to benzene is uncertain in some of the jobs that workers performed. You learn later that 25% of those with bladder cancer had been misclassified as exposed and 30% of those with bladder cancer has been misclassified as not exposed. The same occurred for those without cancer.

Reconstruct the table and calculate the Odds Ratio. (10 points)

	Exposed	Not exposed
Bladder cancer
No cancer

OR =

Would this be consider bias or misclassification? Explain. (5 points)

Part 3

The company performs an audit of your work and finds that, indeed, 25% of those with bladder cancer were missclassified as exposed and 30 %of those with bladder bander had been misclassified as not exposed. HOWEVER, they were able to show that of those without cancer, 20% had been misclassified as exposed and only 10% of those without cancer had been misclassified as not exposed.

Reconstruct the table and calculate the Odds Ratio. (10 points)

	Exposed	Not exposed
Bladder cancer
No cancer

OR =

Would these changes represent bias or misclassification? Explain. (5 points)