In a Gallop Poll, 35% 18-23 year old's stated that they believe in ghosts. Find the probability that out of 16 students aged 18-23:

A. Exactly 5 said they believed in ghosts.
B. Exactly 5 said they do not believe in ghosts.
C.Less than 11 said they do not believe in ghosts.
D. At least 8 said they believe in ghosts.

2 answers

it should be D.
p=.35 q =.65

.35^5 times .65^11 =_____

then you have to multiply that answer by the combination that gets you 16!/11!5! you do that because there are many ways to get those 5 people. It could be the first 5, the last 5, the middle 5 or any possible.

b) .35^11 times .65^5 and then multiply by the same combination that you had above.

c) less than 11 means 0-10 or you can look at it as 11-16 and you would subtract that answer from 1.
This is very complicated and takes a long time to do each possibility. Are you allowed to use a TI-84 calculator or something similar?

At least 8 means 8 -16
.35^8 times .65^8 + .35^9 times .65^7 +.....+ .35^16 times .65^0

for each term you will need the combination that is 16! divided by the factorial of the exponents in each case. Very tedious... so a calculator will help.