Question 815721: According to a survey, college students make an average of 11 calls per day on their mobile phone. Moreover, 80% of the students surveyed indicated that their parents pay for their mobile phone expenses.
If 20 students are selected at random, what is the probability that:
(i) All 20 have their parents pay for their mobile phone expenses?
(ii) At least 8 have their parents pay for their mobile phone expenses?
(iii) No more than 5 students pay for their own mobile phone expenses?
p=0.8 q=0.2
(ii) P(x≥8)= 1- P(x<8)
= 1- 1 - P(0) - P(1)....P(8)???
= 1- 20C0(0.8)^0(O.2)^20.....20C7(O.8)^7(0.2)^13 ???
Can you help me to solve all this questions?im lost...thank you very much for your coorporation.
Answer by ewatrrr(24785)   (Show Source):
You can put this solution on YOUR website!
Hi,
80% of the students surveyed indicated that their parents pay for their mobile phone expenses. 20 students selected at random.
Binomial Probability Distribution Values:
Note: The probability of x successes in n trials is:
P = nCx*  where p and q are the probabilities of success and failure respectively.
In this case p = .8 & q = .2 and n = 20 nCx = 
(i) P(x=20) = (.8)^20(.2)^0 = .0115 0r 1.15%
(ii) At least 8 have their parents pay for their mobile phone expenses?
P(x≥8)= 1- P(x≤7)** TI Calculator: 1 - binomcdf(20,.80,7)= .999998
excel function : 1 - BINOMDIST(7,20,0.8,TRUE)
(iii) No more than 5 students pay for their own mobile phone expenses?
TI Calculator: binomcdf(20,.80,5) = .00000018
excel function : BINOMDIST(5,20,0.8,TRUE)
If You do not have access to a TI Calculator or an Excel Worksheet,
might recommend STATTREK.com as a reference.
|
|
|
