Answer:
651 is the minimum number of people over age 30 they must include in their sample.
Step-by-step explanation:
We are given the following information:
Confidence level = 90%
Significance level = 10%
Maximum error = 0.09
Variance = 1.96
[tex]\text{Standard Deviation} = \sqrt{\text{Variance}} = \sqrt{1.96} = 1.4[/tex]
Formula:
[tex]\text{Error} = z_{critical}\dfrac{\sigma}{\sqrt{n}}[/tex]
Putting all the values,
[tex]z_{critical}\text{ at}~\alpha_{0.05} = \pm 1.64[/tex]
[tex]0.09 = 1.64\times \dfrac{1.4}{\sqrt{n}}\\\\n = (\dfrac{1.64\times 1.4}{0.09})^2 = 650.81 \approx 651[/tex]
651 is the minimum number of people over age 30 they must include in their sample.
