Question

Duiz: Quiz- Chapter 9

Answer 1

Solution :

Given that,

standard deviation = s = 12.9

margin of error = E = 4

a.99 % confidence :

for 99 % CI value of z= 2.58

required sample size n=(zσ/E)²

= ((2.58* 12.9) /4)²

= 69.230

Sample size = 69

b) 90% confidence

for 90% CI value of z= 1.645

sample size n=(zσ/E)²

= ((1.645* 12.9) /4)²

= 28.144

Sample size = 28

we noticed that as confidence level decreases . we need smaller sample size

option-c is correct