An athlete suspected of having used steroids is given two tests that operate independently of each other. Test A has probability 0.9 of being positive if steroids have been used. Test B has probability 0.8 of being positive if steroids have been used. What is the probability that atleast one test is positive if steroids have been used?

0.82

Step-by-step explanation:

given that an athlete suspected of having used steroids is given two tests that operate independently of each other.

Test A has probability 0.9 of being positive if steroids have been used. Test B has probability 0.8 of being positive if steroids have been used.

A and B are independent of each other

Hence P(AB) = P(A) P(B)

Required probability = the probability that atleast one test is positive if steroids have been used

= P(AUB)

= P(A)+P(B)-P(AB)

= 0.9+0.8-0.9*0.8

= 0.82

in problems involving proportions, we can use cross products to test whether two ratios are equal and form a proportion. to find the cross products of a proportion, we multiply the outer terms, called the extremes, and the middle terms, called the means.

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