Guys I got this question in a mock test today at my prep classes. This one REALLY troubled my mind so I took a note of it during the exam. Here is the problem(pardon me for any grammatical mistakes 
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In a test of a certain disease, sickness can be detected with atleast 95% accuracy since out of 100 people who were detected sick were actually sick. If sickness does not occur, it can still be detected with a 95% accuracy since out of 100 people 95 were detected to be free of this disease and only 5 people turned out to be sick. A person was detected to have this sickness so he really must be sick.
Which of the following, if true, weakens the argument?
1) Only fat people get such a sickness
2) Other features of this disease have not been tested
3) This type of testing started lately
4) Under normal circumstances, only two people are sick out of 10,000
)In a test of a certain disease, sickness can be detected with atleast 95% accuracy since out of 100 people who were detected sick were actually sick. If sickness does not occur, it can still be detected with a 95% accuracy since out of 100 people 95 were detected to be free of this disease and only 5 people turned out to be sick. A person was detected to have this sickness so he really must be sick.
Which of the following, if true, weakens the argument?
1) Only fat people get such a sickness
2) Other features of this disease have not been tested
3) This type of testing started lately
4) Under normal circumstances, only two people are sick out of 10,000
