In: Statistics and Probability
First of all check whether all assumptions of binomial distribution is satisfied or not -
The four characteristic of binomial distribution is -
1)The number of observations n=15 is fixed.
2)Each observation is independent.
3)Each observation represents one of two outcomes ("Carry " or "
not carry").
4)The probability of "success" p=0.4 is the same for each
outcome.
To get the probability the respective probabilities
consider, X- Number of business travelers carry either a cell phone
or a laptop
Then X~Bin(15,0.4)
a) probability that three of the travelers carry a cell
phone or laptop= P(X=3) =0.0634
( This is obtained using the excel command
"=Binomdist(number,trail,probability,cumulative)",here
number=3,trail =15 ,probability =0.4 ,cumulative = False in above
command)
b) probability that 12 of the travelers carry neither a
cell nor a laptop= 1- P(X=12) =1-0.0016=0.9984
( This is obtained using the excel command
"=Binomdist(number,trail,probability,cumulative)",here
number=12,trail =15 ,probability =0.4 ,cumulative = False in above
command)
c) probability that at least three of the travelers carry a phone or a laptop= P(X<=3) =0.0905
( This is obtained using the excel command "=Binomdist(number,trail,probability,cumulative)",here number=3,trail =15 ,probability =0.4 ,cumulative = True in above command)