Data Sufficiency (DS) | Re: For what percent of those tested for a certain infection

(1) Of those who tested positive for the infection,1/8 did not have the infection: Insufficient data. No numerical/ratio info is given about those who tested positive.
(2) Of those tested for the infection, 90 percent tested negative : 9/10 -ve & 1/10 +ve. No other information about the certainty is provided. hence insufficient.

1 & 2 together, 1/8 X 1/10 = 1/80 did not have but still tested +ve. 1/10-1/80 = 7/80 did have and tested positive. but no info is provided about those who tested
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