Question

Determine the sample size necessary for estimating the proportion of Ohio teachers that feel anxious about teaching online. Suppose you want to be 99% confidence that the proportion is within 4.25 percentage points of the true proportion. Furthermore, suppose a study from a few years ago showed that 72% of Ohio teachers feel anxious about teaching online.

Answer 1

Solution :

Given that,

= 0.72

1 - = 1 - 0.72= 0.28

margin of error = E = 0.0425

At 99% confidence level the z is,

= 1 - 99%

= 1 - 0.99 = 0.01

/2 = 0.005

Z/2 = 2.58    ( Using z table )

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

= (2.58 / 0.0425)2 * 0.72 * 0.28

=742.93

Sample size = 743