Question

Given: Margin of error (d)= 2.19, Confidence interval (CI) of population mean = 90%, and population standard deviation (σ)= 5 solve for the appropriate sample size.

Answer 1

The critical value for $\alpha = 0.1$ is $z_c = z_{1-\alpha/2} = 1.6449$

$$d=z_c\times\dfrac{\sigma}{\sqrt{n}}$$

$$n=(\dfrac{z_c\times \sigma}{d})^2$$

$$n=(\dfrac{1.6449\times 5}{2.19})^2$$

$$n=14$$