I have some basic questions.

1. If there was a 25% chance of rain on saturday and a 25% chance of rain on sunday what is the % chance of rain for the weekend?

I thought this out, but the text explaination is very vague. I just wanted to know if I am on the right track or if someone can explain this to me better.

the sample space is {SR, RS, SS, RR). But, the elementary outcomes for the sample space are not equal. Let's suppose A is the event it is going to rain on saturday and B is the event it is going to rain on Sunday. Then C is the event it rains on either day.

The Addition Law states that P(C)=P(A)+P(B) - P(A n B)....here P(A n B) would mean probability of rain on both days.

Here is where I get lost. P(A n B)= .25*.25=.0625 (is this then multiplied by two because of the 2 days?) which would give me 12.5%

P(C)=P(A)+P(B) - P(A n B) .... so .25 + .25 - .125= 0.375

or...

P(C)=P(A)+P(B) - P(A n B) .... so .25 + .25 - 0.625 = 0.4375

Please explain...

Also, can you recommend a good text to assist in my studies. My course textbook is Mathematical Statistics and Data Analysis by John Rice, and is a little difficult to follow because I have been away from advanced math for a while. Thanks