5. A history lecture hall class has 15 students. There is a 15% absentee rate per class meeting.

Question

5. A history lecture hall class has 15 students. There is a 15% absentee rate per class meeting. 

a.) Find the probability that exactly one student will be absent from class. (5 points) 

 

 

 

 

 

b.) Find the probability that at least 2 students will be absent from class. (10 points) 

Answer 1

This is a binomial distribution and can be solved with either the calculator or by hand, I will show both:

a) binompdf(15,.15,1) = ₁₅C₁(.15)¹(1-.15)¹⁴=23.12%

b) 1-binomcdf(15,.15,1) (1- because you want 2 or more but the calculator works from the left so you need to take the whole probability 1 or 100% and subtract out what you dont want which is less than 2 (0 and 1)

1-₁₅C₀(.15)⁰(1-.15)¹⁵-₁₅C₁(.15)¹(1-.15)¹⁴=68.14%