Suppose that 86% of the students in a school own a cell phone. If 5 students are surveyed at random,

a) what is the probability that exactly 3 of these students have cell phones?

b) what is the probability that at least 4 of these students have cell phones?

c) what is the probability that less than 4 of these students have cell phones?

Suppose that 86% of the students in a school own a cell phone. If 5 students are surveyed at random, 

a) what is the probability that exactly 3 of these students have cell phones?

P[X=3]= 5C3*(0.86)³(1-0.86)^5-3

P[X=3]= 0.12467

• The probability that exactly 3 of these students have cell phones is 0.12647

b) what is the probability that at least 4 of these students have cell phones?

P[X≥4]= P[X=4] + P[X=5]

P[X≥4]= 5C4*(0.86)⁴(1-0.86)^5-4 + 5C5*(0.86)⁵(1-0.86)^5-5

P[X≥4]= 0.8533

• The probability that at least 4 of these students have cell phones is 0.8533

c) what is the probability that less than 4 of these students have cell phones?

P[X<4] = 1- P[X≥4]

P[X<4] = 1-0.8533

P[X<4] = 0.1467

• The probability that less than 4 of these students have cell phones is 0.1467