Question

Determine what the sample size is within 2% at the 90% confidence level if no preliminary estimate of proportions is known.

Answer 1

Solution :

Given that,

= 0.5

1 - = 0.5

margin of error = E = 2% = 0.02

At 90% confidence level

= 1 - 0.90 = 0.10

/2 =0.05

Z/2 = 1.645 ( Using z table )

Sample size = n = (Z/2 / E)2 * * (1 - )

= (1.645 / 0.02)2 * 0.5 * 0.5

=1691.26

Sample size = 1691