Question

1. Based on a recent Harris poll, 85% of adults know what Twitter is. If five random adults are selected, find:
   1. The probability that none of the five adults know of Twitter

2. The probability that 4 or fewer adults know of Twitter

3. The probability that the number of adults who know of Twitter is at least one

Answer 1

Based on a recent Harris poll, 85% of adults know what Twitter is. If five random adults are selected,

Hence p=85% =0.85

and n=5

here all adults are independent to each other

So this is Binomial Distribution.

X~B(n=5, p=0.85)

a) Probability that none of the five adults know of Twitter is,

Hence P(X=0)=0.000076

b) Probability that 4 or fewer adults know of Twitter is ,

Hence Probability that 4 or fewer adults know of Twitter is 0.5563

c) Probability that the number of adults who know of Twitter is at least one is,

Hence Probability that the number of adults who know of Twitter is at least one is 0.999924