Biostat q on probability plz help thank you

[sadaca]

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hey guys, if anyone has done this q on UW , could u plz help me out in a simple way? Its too mathematical for me, even after many readings of the explanation. Its QD 1284
I appreciate it.

ANS: 1-.95^8

 

[theone435]

hey guys, if anyone has done this q on UW , could u plz help me out in a simple way? Its too mathematical for me, even after many readings of the explanation. Its QD 1284
I appreciate it.

ANS: 1-.95^8

I'm trying to figure out a way to explain it in a way that is different from the explanation. It would help if you told us how you went about trying to solve the question.
But when you look at probabilities, a probabilities of an event happening and an event not happening add up to 1 (100%). So lets have the event represented by x meaning the event not happening is (1-x).

And when you're trying to combine the probabilities of 2 different things happening you multiply them. So here you have the probability of the test being negative 1 time as .95. If you want to know the probability of the test being negative twice, then you do .95 * .95. And if you want the the probability that the test is negative 8 times in a row, then you do .95 ^8 power.

But the question is asking for the probability that it is not negative 8 times in a row so you have to do (1-x) so you get 1 - .95^8.

 

[sadaca]

thank you =)