Question

If the chance that a student chosen at random has an IPhone is 30%, what is the chance that out of a group of 30 students chosen at random the number with an IPhone is more than 12?

Use z-values to express this answer.

Answer 1

Solution :

Given that,

p = 0.30

q = 1 - p =1-0.30=0.70

n = 30

Using binomial distribution,

= n * p = 30*0.30=9

= n * p * q = 30*0.30*0.70=2.50998

Using continuity correction

,P(x > 12) = 1 - P(x <12 )

= 1 - P((x - ) / < (12-9) / 2.50998)

= 1 - P(z <1.20 )   

Using z table   

= 1-0.8849

probability= 0.1151