Question

                         Positive       Negative

Influenza A.         360.              7
no influenza A.      6.               1110

find the probability of a subject with a positive test result given that the subject does have influenza A

find the probability of selecting a subject with a negative test result given that the subject does not have influenza a

Answer 1

	Positive	Negative	Total
Influenza A	360	7	367
no influenza A	6	1110	1116
Total	366	1117	1483

find the probability of a subject with a positive test result given that the subject does have influenza A

P[ positive test | does have influenza A ] = number of positive test and person does not have influenza A / number of does have influenza A

P[ positive test | does have influenza A ] = 6/1116

P[ positive test | does have influenza A ] = 0.005376

find the probability of selecting a subject with a negative test result given that the subject does not have influenza a

P[ negative test | does have influenza A ] = number of negative test and person does not have influenza A / number of does have influenza A

P[ negative test | does have influenza A ] = 1 - P[ positive test | does have influenza A ]

P[ negative test | does have influenza A ] = 1 - 0.005376

P[ negative test | does have influenza A ] = 0.994624