Question

Past records show that at a certain college 20% of the students who began as economics majors changed majors before they graduated. An incoming freshmen class has 110 beginning economics majors. What is the probability that at least 15% of the incoming economics majors change their major before graduation?  

Answer 1

Solution

Given that,

p = 0.20

1 - p = 1-0.20=0.80

n = 110

= p =0.20

=  [p( 1 - p ) / n] = [(0.20*0.80) /110 ] = 0.0381

P( > 0.15) = 1 - P( <0.15 )

= 1 - P(( - ) / < (0.15-0.20) / 0.0381)

= 1 - P(z <-1.31 )

Using z table

= 1 -0.0951

=0.9049

probability=0.9049