fozzzy wrote:

isn't this question asking for 2 variables? I got the answer E

Attachment:

Infection tests.jpg [ 122.08 KiB | Viewed 4519 times ]
I think this problem goes beyond 2 variables. You can use the overlapping sets table, as there can be 4 possibilities for patient to be infected/not-infected:

Tests are Positive & Accurate -> Patient is infected

Tests are Positive & Inaccurate -> Patient is NOT infected

Tests are Negative & Accurate -> Patient is NOT infected

Tests are Negative & Inaccurate -> Patient is infected

Our objective is to identify the value of cell marked in yellow (i.e. Accurate tests) hence find its ratio to TOTAL tests (i.e. % Accuracy)

(1) Of those who tested positive for the infection,1/8 did not have the infection.

INSUFFICIENT: Refer to the diagram, this gives no info to derive the value for yellow cell (i.e. Accurate tests)

(2) Of those tested for the infection, 90 percent tested negative.

INSUFFICIENT: Refer to the diagram, this gives no info to derive the value for yellow cell (i.e. Accurate tests)

Combining (1) & (2)

INSUFFICIENT: Even after combining the statements are INSUFFICIENT to derive the value for yellow cell (i.e. Accurate tests)

Hence Choice(E) is the answer. _________________

Thanks,

Prashant Ponde

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