Quizz 3 Question 2-3

Quizz 3 Question 2-3

by Taha Zakariya -
Number of replies: 3

Hello,

I'd like to ask about the questions that concern the application of Viterbi from the last quizz.

Having constructed the viterbi graph, I get for example for w2 the two following values: 0.0144 for N and 0.0032 for V (at the end the most probable sequence goes through N). We saw in the course that Viterbi keeps the max value, so I don't get why for "the node associated with V for the word "w2" " the answer is 0.0032. Same thing for the next one, we keep the lower value which is also the one that isn't included in the most probable sequence. Could you please give me some clarification on this matter?

Thanks.

In reply to Taha Zakariya

Re: Quizz 3 Question 2-3

by Deniz Bayazit -
I think this was answered today in-person. Let me know if something is still not clear!
In reply to Deniz Bayazit

Re: Quizz 3 Question 2-3

by Issam Arabi -
Can you explain how we got the answer for q2 and q3?
In reply to Issam Arabi

Re: Quizz 3 Question 2-3

by Jean-Cédric Chappelier -
you have to "accumulate" (multiply) the probabilities along the path (Pinit * Pemit_1 + Ptransition_1_to_2 * Pemit_2 * Ptransition_2_to_3 * Pemit_3 *....), taking the max at each step.
In your case:
Q2 : 0.8 * 0.2 * 0.1 * 0.2 = .0032 (no max to take here since no ambiguity)
Q3 : 0.8 * 0.2 * max(0.9 * 0.1 * 0.5 , 0.1 * 0.2 * 0.4) * 0.3 = 0.8 * 0.2 * 0.9 * 0.1 * 0.5 * 0.3 = 0.00216