Question

Suppose that 200 students are randomly selected from a local college campus to investigate the use of cell phones in classrooms. When asked if they are allowed to use cell phones in at least one of their classes, 40% of students responded yes. Using these results, with 95% confidence, the margin of error is 0.068. How would the margin of error change if the sample size increased from 200 to 400 students?

Answer 1

It would change to 0.04802

Explanation:

from this question we have that n became 400

40% of 400

= 160

p* = 160/400

= 0.4

1 - p* =

= 1 - 0.4

= 0.6

at confidence level,

1 - 0.95

= 0.05

alpha/2 = 0.025

z= 1.96

margin of error. E

= 1.96 x √[(0.4 x 0.6)/400]

= 1.96 x 0.0245

= 0.04802

M.E = 0.04802