# Venn diagram

• October 10th 2010, 07:52 PM
noid
Venn diagram
2.
Social networking Web sites in the United Kingdom. In the United States, MySpace and FaceBook are considered the two most popular social networking Web sites. In the United Kingdom (UK), the competition for social net- working is between MySpace and Bebo. According to Nielsen/NetRatings (April 2006), 4% of UK citizens visit MySpace, 3% visit Bebo, and 1% visit both MySpace and Bebo.
a. DrawaVenndiagramtoillustratetheuseofsocialnet- working sites in the United Kingdom.
b. Find the probability that a UK citizen visits either the MySpace or Bebo social networking sites.
c. Useyouranswertopartbtofindtheprobabilitythata UK citizen does not visit either social networking site.

Am i right/wrong? suggestions?
• October 10th 2010, 08:13 PM
harish21
Note that:

$P(A \cup B) = P(A)+P(B)-P(A \cap B)$
• October 10th 2010, 08:28 PM
noid
Well, how does the 1% apply in this case?

If A is .04 + .01
and B is .03+.01

Wouldnt it be .04+.03+0.01+ 0.01 - 0.01?

Thus equal to 0.08?

*OR* is it that the .01 (1 percent) is already included in the .04+0.3?
• October 10th 2010, 08:34 PM
harish21
$P(A)=0.04$

$P(B)=0.03$

$P(A \cap B) = 0.01$

$P(A \cup B) = P(A)+P(B)-P(A \cap B) = 0.04+0.03-0.01=0.06$

----------------------------------------------------------------------------------------------

$P(A_{\mbox{only}})= P(A)-P(A \cap B) = 0.04-0.01=0.03$

$P(B_{\mbox{only}})= P(B)-P(A \cap B) = 0.03-0.01=0.02$

$P(A \cup B) = P(A_{\mbox{only}})+P(A_{\mbox{only}})+P(A \cap B) = 0.03+0.02+0.01=0.06$
• October 10th 2010, 08:44 PM
noid
Ah, I understand now. Thank you very much, from what I understand I have part a right, now i have part b right, and part c? Can it then be said that A XOR B = 1.00 - .06, because the probability of use is 6% thus the probability of non use is the compliment (.94)?
• October 10th 2010, 08:58 PM
harish21
(Yes)
• October 10th 2010, 09:02 PM
noid
Thank you very much, im new to the forum, how do i give you a "thanks" to your count? I like the way you help, i feel like if im presented with such a question on my midterm i should do just fine :).

Now only if I could get help to figure out the correct answers to my other questions ( in the advanced statistics subforum).(Hi) The midterm is about a week away and getting these key concepts right from these questions would do wonders to my success.
• October 10th 2010, 09:04 PM
harish21
look at the bottom left of the post, you should see the thanks button!