## Bayes Rule Diagram - Intro to Machine Learning

• 0:00 - 0:05
What we really said that we had a situation that prior
• 0:05 - 0:10
a test is a certain sensitivity and a certain specificity.
• 0:10 - 0:15
When you receive say a positive test result, what you do is you take your prior,
• 0:15 - 0:19
you multiply in the probability of this test result.
• 0:19 - 0:24
Given C, and you multiply in the probability of the test result given not C.
• 0:24 - 0:28
So this is your branch for the consideration that you have cancer.
• 0:28 - 0:32
This is your branch for the consideration you have no cancer.
• 0:32 - 0:36
When you're done with this, you arrive at a number that now combines the cancer
• 0:36 - 0:38
hypothesis with the test result.
• 0:38 - 0:41
Both for the cancer hypothesis and the not cancer hypothesis.
• 0:43 - 0:46
Now what you do, you add those up.
• 0:46 - 0:50
And they normally don't add up to one.
• 0:50 - 0:51
You get a certain quantity,
• 0:51 - 0:55
which happens to be the total probability that the test is what it was.
• 0:55 - 0:57
This case positive.
• 0:57 - 0:59
And all you do next is divide or
• 0:59 - 1:04
normalize this thing over here by the sum over here.
• 1:04 - 1:06
And the same on the right side.
• 1:06 - 1:08
The divider is the same for
• 1:08 - 1:13
both cases because this is your cancer range, your non cancer range.
• 1:13 - 1:15
But this guy doesn't rely on the cancer variable anymore.
• 1:15 - 1:20
What you now get out is the desired posterior probability, and
• 1:20 - 1:24
those add up to one if you did everything correct as shown over here.
• 1:24 - 1:26
This is your algorithm for Bayes Rule
Title:
Bayes Rule Diagram - Intro to Machine Learning
Description:

more » « less
Video Language:
English
Team:
Udacity
Project:
ud120 - Intro to Machine Learning
Duration:
01:27
 Udacity Robot edited English subtitles for Bayes Rule Diagram - Intro to Machine Learning Udacity Robot edited English subtitles for Bayes Rule Diagram - Intro to Machine Learning Cogi-Admin edited English subtitles for Bayes Rule Diagram - Intro to Machine Learning

# English subtitles

## Revisions Compare revisions

• API
Udacity Robot
• API
Udacity Robot
• API