Review the Unit 6 belief network available for download on the Reading Assignment page. The belief network extends the electrical domain to include an overhead projector.
Answer the following questions about how knowledge of the values of some variables would affect the probability of another variable:
- Can knowledge of the value of Projector_plugged_in affect your belief in the value of Sam_reading_book? Explain your answer.
No, because the value of Sam_Reading_Book doesn’t depend on Projector_plugged_in. Sam_Reading_Book depends on:
- Room_Light_On
- Power_in_Building
- Light_Switch_On
- Can knowledge of Screen_lit_up affect your belief in Sam_reading_book? Explain your answer.
- Can knowledge of Projector_plugged_in affect your belief in Sam_reading_book given that you have observed a value for Screen_lit_up? Explain your answer.
These values are not directly related. If Sam is sitting in the same room where the projector is used, then the the value of Screen_lit_up affect the belief in Sam_reading_book, because projector screen cannot be lit up only if the room light is off, and when light is off, Sam wouldn’t be able to read a book. Also, it is possible that the screen is off and Sam is either reading or not reading a book
- Which variables could have their probabilities changed if just Lamp_works was observed?
The value of the following variables depend on Lamp_Works:
- Projector_Lamp_On
- Screen_Lit_up
- Ray_Says_Screen_is_Dark
- Which variables could have their probabilities changed if just Power_in_prjector was observed?
Same as the previous variable, Lamp_Works, Power_in_Projector affects the following probabilities:
- Projector_Lamp_On
- Screen_Lit_up
- Ray_Says_Screen_is_Dark
