Question

If a denotes some​ event, what does upper a overbara ​denote? if ​p(a)equals=0.9930.993​, what is the value of ​p(upper a overbara​)? if ​p(a)equals=0.9930.993​, is upper a overbara ​unlikely?

Answer 1

P(A) = 0.993 is the probability of event A
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P(A) is the probability of not A (note that I am trying to place a bar over A. I hope you can see it, else it is because the editor did not show it as I intended)

Then, use the fact that the probability of A plus the probability not A is equal to 1:
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=> P(A) + P(A) = 1
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=> P(A) = 1 - P(A) = 1 - 0.993 = 0.007

So, the answers are:
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1) P(A) = 0.07
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2) Yes, A is unlikely because its probability is very low.