Contents

## Is Double DQN better than DQN?

There is no thorough proof, theoretical or experimental that Double DQN is better then vanilla DQN. There are a lot of different tasks, paper and later experiments only explore some of them. What practitioner can take out of it is that on some tasks DDQN is better.

## What is the difference between Q learning and double Q learning?

Notice that in Q-Learning, Q(A, Left) is positive because it is affected by the positive rewards that exist at state B. Because of this positive value the algorithm is more interested in taking the Left action hoping to maximize the rewards. In Double Q-Learning Q1(A, Left) and Q2(A, Left) start slightly negative.

**Is Double DQN off policy?**

The off-policy algorithms learn a value function independently from the agent’s decisions. This means that the behavior policy and the target policy can be different. The two algorithms that we will see in this part, Double DQN and Dueling DQN, are also model free and off-policy.

**Why Deep Q learning is better than Q learning?**

A core difference between Deep Q-Learning and Vanilla Q-Learning is the implementation of the Q-table. Critically, Deep Q-Learning replaces the regular Q-table with a neural network. Rather than mapping a state-action pair to a q-value, a neural network maps input states to (action, Q-value) pairs.

### Is Q learning biased?

Q-learning suffers from overestimation bias, because it approximates the maximum action value using the maximum estimated action value. We empirically verify that our algorithm better controls estimation bias in toy environments, and that it achieves superior performance on several benchmark problems.

### What’s the difference between dueling DQN and Double DQN?

The difference in Dueling DQN is in the structure of the model. The model is created in a way to output the formula below: Here, the V (s) stands for the Value of state s and A is the Advantage of doing action a while in state s. The Value of a state is independent of action. It means how good is it to be in a particular state.

**How is Double DQN used in deep reinforcement learning?**

For training the neural network the targets would be the Q-values of each of the actions and the input would be the state that the agent is in. Double DQN uses two identical neural network models. One learns during the experience replay, just like DQN does, and the other one is a copy of the last episode of the first model.

**Are there any algorithms that improve on DQN?**

In this part, we will see two algorithms that improve upon DQN. These are named Double DQN and Dueling DQN. But first, let’s introduce some terms we have ignored so far. All the reinforcement learning (RL) algorithms can be classified in several families.

#### What is the target Q-value in dqns?

In a DQN, which uses off-policy learning, they represent a refined estimate for the expected future reward from taking an action a in state s, and from that point on following a target policy. The target policy in Q learning is based on always taking the maximising action in each state, according to current estimates of value.