Question

Which expression should you simplify to find the 90% confidence interval,

Answer 1

Answer:

$0.45 - 1.96\sqrt{\frac{0.45(1-0.45)}{36}}=0.287$

$0.45 + 1.96\sqrt{\frac{0.45(1-0.45)}{36}}=0.613$

And we can conclude at 95% of confidence that the true proportion of interest for this case is between 0.287 and 0.613

Step-by-step explanation:

The estimated proportion of interest is $\hat p=0.45$

We need to find a critical value for the confidence interval using the normla standard distributon. For this case we have 95% of confidence, then the significance level would be given by $\alpha=1-0.95=0.05$ and $\alpha/2 =0.025$. And the critical value is:

$z_{\alpha/2}=-1.96, z_{1-\alpha/2}=1.96$

The confidence interval for the true population proportion is interest is given by this formula:  

$\hat p \pm z_{\alpha/2}\sqrt{\frac{\hat p (1-\hat p)}{n}}$

Replacing the values provided we got:

$0.45 - 1.96\sqrt{\frac{0.45(1-0.45)}{36}}=0.287$

$0.45 + 1.96\sqrt{\frac{0.45(1-0.45)}{36}}=0.613$

And we can conclude at 95% of confidence that the true proportion of interest for this case is between 0.287 and 0.613