Question

Assume that 65% (0.65) of all registered voters vote in a US presidential election (population characteristic). A random sample of 1000 registered voters is taken. What is the probability that between 63% (0.63) to 67% (0.67) in the sample voted?

Answer 1

  

Solution

Given that,

p = 0.65

1 - p = 0.35

n = 1000

= p = 0.65

=  [p ( 1 - p ) / n] = [(0.65 * 0.35) / 1000] = 0.01508

= P[(0.63 - 0.65) / 0.01508 < ( - ) / < (0.67 - 0.65) / 0.01508]

= P(-1.13 < z < 1.13)

= P(z < 1.13) - P(z < 1.13)

= 0.7415