1. ## Bionomial Distribution

What kinds of Websites do males aged 18-34 visit? About 50% of male internet users in this age group visit an auction site such as eBay at least once a month. Interview a random sample of 12 male Internet users aged 18 to 34.

A) What is the distribution of the number who have visited an online auction site in the past month?

B) What is the probability that exactly 8 of the 12 have visited an auction site in the past month? If you have software, also find the probability that at least 8 of the 12 have visited an auction site in the past month.

This is probably the most difficult chapter during my course. :/

2. Originally Posted by Gicco
What kinds of Websites do males aged 18-34 visit? About 50% of male internet users in this age group visit an auction site such as eBay at least once a month. Interview a random sample of 12 male Internet users aged 18 to 34.

A) What is the distribution of the number who have visited an online auction site in the past month?

B) What is the probability that exactly 8 of the 12 have visited an auction site in the past month? If you have software, also find the probability that at least 8 of the 12 have visited an auction site in the past month.

This is probably the most difficult chapter during my course. :/
Just write out all the information you have and plug it in. The information below should be more than enough to get you started.

a) Binomial with n=12, y=8, and p=0.5.

b)$\displaystyle P(Y=8)=\left(\begin{array}{cc}12\\8\\\end{array}\r ight)(0.5)^{8}(1-0.5)^{12-8}=$

and for the second you part you need to compute,

$\displaystyle P(Y\geq\\8)=\sum_{y=8}^{12}\left(\begin{array}{cc} 12\\y\\\end{array}\right)(0.5)^{y}(1-0.5)^{12-y}=$

3. I think you meant....

$\displaystyle P(Y\geq\\8)=\sum_{y=8}^{12}\left(\begin{array}{cc} 12\\y\\\end{array}\right)(.5)^{y}(.5)^{12-y}$

4. Originally Posted by matheagle
I think you meant....

$\displaystyle P(Y\geq\\8)=\sum_{y=8}^{12}\left(\begin{array}{cc} 12\\y\\\end{array}\right)(.5)^{y}(.5)^{12-y}$
Thanks again. I need to stop copy and pasting my work without review! Sorry for my orginal post Gicco, I hope you found the error. The summation was useless before the edit.