College Statistics
Background information:
鈥淯SA Today stated that 鈥業nternal surveys paid for by directory assistance providers show that even the most accurate companies give out wrong numbers 15% of the time.鈥? Assume that you are testing such a provider by making 10 requests and also assume that the provider indeed gives the wrong telephone number 15% of the time."
a) Find the probability of getting AT MOST one wrong number.
b) If you do get at most one wrong number, does it appear that the rate of wrong number is not 15%, as claimed?
I solved a) as
n=10, x=0 and 1, p=0.15 (15%)
P (x<=1)= P (0) + P (1)
=0.196874 + 0.347425
=0.5443
My questions are two-fold:
1) Is my part a) calculations right, and
2) I am pretty sure my answer to part a) is wrong, because it is very UNLIKELY that the companies give wrong numbers 54% of the time!!!!
Please help!!!!! Where did I go wrong?? Thank you everyone! P(0) = 0.85^10 = 0.196874
P(1) = 0.15 * 0.85^9 * 10 = 0.347425
So P(0) + P(1) = 0.5443, like you said. However, this doesn't mean that the company gave wrong answers 54% of the time, it means that OUT OF 10 TRIES, they gave fewer than 2 wrong answers 54% of the time.
So no, this doesn't affect the claim of 15% wrong answers.
I hope this helps! okay!! does anyone know if the story on the Smith Sisters is REAL!
Don't stop reading you will regret it!
girl meets a boy on a messenger
crazy1 86: hey baby!!!
h0tNsPiCy91: who is this???
crazy1 86: ur secret admirer!!!!!
h0tNsPiCy91: oh really.... quit lyin! who is this???
crazy1 86: i loved u the first time a stared in your eyes...
crazy1 86: i think about u everyday... you are my dream come true.
crazy1 86: we met once! i dont think u remember tho.
crazy1 86: i cut myself because the pain takes away my feelings of u.
crazy1 86: u will see me sometime tonight....
h0tNsPiCy91: ..WHO IS THIS!?!?!?
crazy1 86:dont worry.... ill take very good care of you...
crazy1 86 had signed off.
The girl was so scared she locked all her doors and windows. She made sure her room was secured. She wasn't sure if it was a joke or for real. She didn't know when he was going to come. The girl was so frightened she decided to sleep with her little sister. The girl dozed off quickly.
Then she heard a knock on the window. The girl slowly walked to the window. It started knocking louder. The girl looked through the windows and saw nothing... just some of the tree branches. The girl went back to bed with her sister. The bed was wet and had a pretty horrid smell. Maybe her sister wet the bed... the girl checked and found blood everywhere. The girl panicked. She didn't know what to do. She ran and hid in the closet in case the killer was there for her. While looking through the cracks of the closet the girl saw a shadow. It was dark, so she couldn't figure out who it was. She started to get more frightened. The shadow crept closer to the closet. The girl closed her eyes as if it was a dream. Then suddenly he opened the closet door and pulled her out.
Her parents found her dead the next morning. She was completely skinned and hanging in her sister's closet. The younger sister was also found skinned and dead.
PART 2...
Two years after the Smith sisters deaths, the parents had a baby boy. The girl's room became a guest room and the little sister's room where the murder took place became the baby's room. The baby grew up to be a successful kid.
One night he was on the computer and received an instant message.
h0tNsPiCy91: Hey lil bro!!!
2seXay4u: Who the eff is this?
h0tNsPiCy91: It's your big sis.
2seXay4u: I never had a sister. I'm an only child.
2seXay4u: This is some kinda joke, huh?
h0tNsPiCy91: Mom and dad never told you?
h0tNsPiCy91: I died 15 years ago with your other older sister.
h0tNsPiCy91: We were murdered in your room which was once my little sister's room. She was killed in bed when I was sleeping. I was killed in the closet and skinned to death.
2seXay4u: Quit lying. I never had a sister. If I did my parents would have told me. Whatever. Your stupid.
h0tNsPiCy91: You don't believe me? Well if you wanna look in your closet floor.
h0tNsPiCy91: I carved my name and the time and date I was being murdered. Then I carved my little sister's name.
h0tNsPiCy91: If you don't believe me little brother check the internet. Google on ''Smith sisters murdered anonymously''.
h0tNsPiCy91: I gtg little brother. I love you and mom and dad soo much. I can't believe they kept us a secret from you.
The boy checked the closet. He saw the carvings. Was it true? He surfed the internet and information was there about the anonymous murder in the house. The next morning the boy went downstairs. It was so quiet. Maybe his parents were sleeping. Hours later the boy found his parents in their closet skinned and hanged. Then he found more carvings on the ground. They said ''I TOLD YOU I WASN'T LYING LITTLE BROTHER, I LOVED MOM AND DAD.... BUT THEY KEPT ME A SECRET. I CAN'T BELIEVE IT. WELL I'M FREE FROM THIS COLD WORLD, I WON'T HURT YOU LIKE I HURT THEM. I LOVE YOU!"
- LISA SMITH
This is a death chain letter. If you don't repost this in the next hour, the parents will kill you at night. They will kill you!
DON'T BELIEVE ME? LOOK IT UP IN GOOGLE!
:( :( part A:
try using
15C0(.15)^0(.85)^15 + 15C1(.15)^1(.85)^14
-binomial therom |
