SOLUTION: At Med U. the failure rate is 20%. Of 15 students registered in the freshman class; What is the probability that they all pass? What is the probability that a least 1 fails? Ho

 

Hi,

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(failing) = .20 and q(passing) = .80   |the failure rate is 20%.

nCx = 

Of 15 students registered in the freshman class;

 P(all pass) = (.80)^15 = .0352

P(at least 1 fails) = 1 - P(none failing) = 1 - .0352 = .9648

How many freshman are likely to pass? .80*15 = 12



An algebra class has 18 girls and 14 boys. 

Five tickets to a concert have just been made available to the class. 

The students to get the tickets will be chosen at random.

What is the probability that:

a) five girls are chosen = 18C5/32C5 = 8568/201,376 = .0425

  nCx =   18C5 =  18!/(5!13!) and 32C5 = 32!/5!27!

These can be found with a calculator that has a factorial function.



b) five boys are chosen = 14C5/32C5 = 2002/201,376 = .0099

c) at least 1 girl is chosen? 1 - P(all boys) = 1 - .0099 = .9901

d) How many girls are likely to be chosen? (18/32)*5 = 2.8