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# What is the prior probability P(C = ‘no’) ? how i can find prior probability in this table ? Naïve

Member Posts: 6 Contributor I

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Administrator, Moderator, Employee, RapidMiner Certified Analyst, RapidMiner Certified Expert Posts: 955 Unicorn
Hi,

Here's RapidMiner founder Ingo explaining the algorithm:

If you look at the model description, it says:

# SimpleDistribution

```Distribution model for label attribute Play

Class no (0.357143)
4 distributions

Class yes (0.642857)
4 distributions```
These are exactly the fractions of the values in the entire distribution - the prior probability of the class in the training data.

The numbers you see in the table can be interpreted as "the fraction of the data where Outlook = overcast and Play = yes".

Regards,
Balázs
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Moderator, RapidMiner Certified Analyst, RapidMiner Certified Expert, Member Posts: 1,635 Unicorn
If you look at the table, you can see that the probabilities shown will total to 1 (not accounting for rounding) for each class for each attribute.  So there are 4 possible values for the outlook attribute (rain, overcast, sunny, unknown) and 2 classes (yes/no) and the sums for each set will total to 1.
Brian T.
Lindon Ventures
Data Science Consulting from Certified RapidMiner Experts