Hello I’m not able to find a solution that matches the given options for what the exercise asks:

The only way I was able to find a matching solution was calculating: *“Probability that a user experienced a bug, given that he tested Version B”* and not what the exercise ask i.e. *“Probability that a user tested version B, given they experienced a bug during testing”*.

Is there a typo in the exercise or do I need to study more ?

I think both statements mean the same!

Why are they the same? Let’s say P(B) is the probability of a user testing Version B and E is the event of a bug:

*Probability that a user experienced a bug, given that he tested Version B”*

P(E|B)=P(E and B) / P(B) = 1500/9000 * 9000/5000 = 1500/5000 = 3/10=30%

While:

*“Probability that a user tested version B, given they experienced a bug during testing”* .

P(B|E)=P(E and B) / P(E) = 1500/9000 * 9000/3000 = 1500/3000 = 1/2=50%

What am I missing?

Thanks!