Equality in conditional probability

In summary, the conversation discusses the relationship between P(x,\theta|D) and P(x|\theta,D) in Dudas Pattern Classification. The speaker mentions not being able to find justification for why they are equal and asks for clarification on the notation. The expert explains that P(x,\theta|D) is the probability of x and \theta given D, while P(x|\theta,D) is the probability of x given D and \theta. The expert also mentions that Bayes rule can be used to write P(x,\theta|D) in terms of P(x|\theta,D).
  • #1
Avatrin
245
6
Hi

In Dudas Pattern Classification, he Writes that [itex] P(x,\theta|D) [/itex] can always be written as [itex] P(x|\theta,D)P(\theta|D) [/itex]. However, I cannot find any justification for this. So, why are these Equal?
 
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  • #2
Avatrin said:
Hi

In Dudas Pattern Classification, he Writes that [itex] P(x,\theta|D) [/itex] can always be written as [itex] P(x|\theta,D)P(\theta|D) [/itex]. However, I cannot find any justification for this. So, why are these Equal?
How are ##P(x,\theta|D)## and ##P(x|\theta,D)## defined? I took a lot of classes in probability and mathematical statistics, but it has been many years ago. I don't recall seeing this notation.
 
  • #3
Mark44 said:
How are ##P(x,\theta|D)## and ##P(x|\theta,D)## defined? I took a lot of classes in probability and mathematical statistics, but it has been many years ago. I don't recall seeing this notation.

[itex]P(x,\theta|D)[/itex] is the probability of [itex]x[/itex] and [itex]\theta[/itex] given [itex]D[/itex] which is our sample set. [itex]P(x|\theta,D)[/itex] is the probability of [itex]x[/itex] given [itex]D[/itex] and [itex]\theta[/itex]. [itex]x[/itex] is a random variable, and [itex]\theta[/itex] is a parameter which we are estimating by considering it to be a random variable.
 
  • #4
Start by writing ##P(x,\theta/D)## using Bayes rule.
 

1. What is conditional probability?

Conditional probability is the likelihood of an event occurring given that another event has already occurred. It is denoted as P(A|B), where A is the event of interest and B is the event that has already occurred.

2. How does equality in conditional probability relate to fairness?

Equality in conditional probability is a measure of fairness in decision making. It ensures that the probability of an outcome is the same regardless of different characteristics or conditions that may be present.

3. Can you provide an example of equality in conditional probability?

One example of equality in conditional probability is in the hiring process. If the probability of a male candidate being hired is the same as the probability of a female candidate being hired, regardless of their gender, then there is equality in conditional probability.

4. How is equality in conditional probability calculated?

Equality in conditional probability is calculated by comparing the conditional probabilities of different groups. If the conditional probabilities are equal, then there is equality in conditional probability.

5. Why is equality in conditional probability important in scientific research?

Equality in conditional probability is important in scientific research because it ensures that the results are not biased or affected by certain characteristics or conditions. It allows for fair and unbiased conclusions to be drawn from the data.

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