Question

Polly's Polls asked 1850 second year college students if they still had their original major . What is the probability that Polly's Polls random sample will give a result within 1% of the true value?

Answer 1

Sample size, n = 1850

Since there is no prior estimate of p, assume that p = 0.5

P( < A) = P(Z < (A - )/)

= p = 0.5

=

=

= 0.0116

P(sample will give a result within 1% of the true value) = P(0.49 < p < 0.51)

= P(p < 0.51) - P(p < 0.49)

= P(Z < (0.51 - 0.50)/0.0116) - P(Z < (0.49 - 0.5)/0.0116)

= P(Z < 0.86) - P(Z < -0.86)

= 0.8051 - 0.1949

= 0.6102