Probability in a Bell Curve Lets assume that a phone number lies in one of three pages with equal probability (1/3).  
The probability of selecting the pages follows a Bell Curve with probabilities as : 

.2    .6    .2 

Now the user selects a page. What is the probability that the phone number is on that page
 A: Hint: It might help to think about these two similar problems first:
A)
Let's assume that one of three pages is selected from a phone book with probabilities 

.2    .6    .2

The user selects a page. Now we throw a die and write a phone number on one of the three pages with equal probability (1/3).
What is the probability that we write the phone number on the selected page?
When you feel sure about the answer to that one, consider
B) 
Let's assume that we throw a die and write a phone number on one of three pages of a phone book with equal probability (1/3).
Now the user selects one of the three pages from the phone book with probabilities 

.2    .6    .2

What is the probability that the page that has the phone number written on it is selected?
What difference do you think it could make whether we throw the die before or after the selection? 
Then, when you feel sure about the answer to that one, think about what difference you think it could make whether we throw a die before the selection or the number is already there with the same probabilities as given by the die.
