# Thread: Binomial Probability Questions

1. ## Binomial Probability Questions

Hi, I have a couple questions concerning Binomial Probabilities that I have just not been able to figure out! I've been flipping through my statistics book and have found nothing that covers the problems in question. Any help from you math geniuses would be much appreciated.

1) It has been found that 20% of students who enroll in an introductory statistics class withdraw before the end of the semester. In a class of 15 students, what is the probability that:

-Between 2 and 6 students withdraw

-Less than 4 students withdraw

2) It is estimated that in 90% if criminal trials, the jury will reach the correct verdict. SUppose 100 cases are selected at random, what is the probability that:

-At least 93 cases had the correct verdict?

-Fewer than 85 cases had the correct verdict?

Any help you guys could offer would really be appreciated. Thank you in advance!

2. Those problems are just routine if you have studied the corresponding theory. For example, for your first question:

$\displaystyle P(2\leq \xi \leq 6)=\sum_{k=2}^{6}\binom{15}{k}(0,2)^k(0,8)^{15-k}$

Fernando Revilla