If it is snowing, there is an 80% chance that class will be canceled. If it is not snowing, there is a 95% chance that class will go on. Generally, there is a 5% chance that it snows in NJ in the winter. If we are having class today, what is the chance that it is snowing?

Respuesta :

Answer:

[tex]P(S|\bar{C} ) = 0.1739[/tex]

Step-by-step explanation:

We define the probabilistic events how:

S: Today is snowing

C: The class is canceled

If it is snowing, there is an 80% chance that class will be canceled, it means

P( C | S ) = 0.8  conditional probability

If it is not snowing, there is a 95% chance that class will go on

[tex]P( \bar{C} | \bar{S}) = 0.95[/tex]

and P(S) = 0.05

We need calculate

[tex]P( S |\bar{C} ) = \frac{P(\bar{C} | S) P(S)}{P(\bar{C})}[/tex]

[tex]P(\bar{C}) = P( \bar{C}|S)P(S) + P( \bar{C}|\bar{S})P(\bar{S})[/tex]

How

[tex]P(C | S) = 0.8[/tex]  then  [tex]P( \bar{C} | S) = 0.2[/tex]

[tex]P (\bar{C})[/tex] = (0.2)(0.5) + (0.95)(0.5)

                                =0.575

[tex]P(S |\bar{C} ) = \frac{(0.2)(0.5)}{(0.575)}[/tex]

[tex]P(S|\bar{C} ) = 0.1739[/tex]