Robot States and Sensors

Question

Suppose we have a robot that can be in one of two states: state 1 or state 2. The robot moves between states according to the following rules:

If the robot is in state 1, it has a 70% chance of staying in state 1 and a 30% chance of transitioning to state 2.

If the robot is in state 2, it has a 60% chance of staying in state 2 and a 40% chance of transitioning to state 1.

The robot has two sensors: sensor 1 and sensor 2. The sensors are not perfect and sometimes give incorrect readings. The emission probabilities for each sensor are as follows:

If the robot is in state 1, sensor 1 gives the correct reading with a probability of 0.8 and an incorrect reading with a probability of 0.2. If the robot is in state 2, sensor 1 gives the correct reading with a probability of 0.4 and an incorrect reading with a probability of 0.6.

If the robot is in state 1, sensor 2 gives the correct reading with a probability of 0.3 and an incorrect reading with a probability of 0.7. If the robot is in state 2, sensor 2 gives the correct reading with a probability of 0.9 and an incorrect reading with a probability of 0.1.

Assume that the robot starts in state 1 with equal probability and generates the following sensor readings over time:

sensor 1: correct, correct, incorrect

sensor 2: incorrect, correct, correct

What is the most likely sequence of states that the robot went through to generate these observations?

Answer 1

I assumed you meant the robot starts in state 1 or 2 with equal probabilities and I also assumed that two sensor's readings are independent of each other.

The answer is State 1, State 1, and State 2.

Please find the worksheet here.

Google Sheet