Answer:
The lower bound of the confidence interval is 0.6922.
Step-by-step explanation:
We have to calculate a 94% confidence interval for the proportion.
The sample proportion is p=0.7167.
[tex]p=X/n=860/1200=0.7167[/tex]
The standard error of the proportion is:
[tex]\sigma_p=\sqrt{\dfrac{p(1-p)}{n}}=\sqrt{\dfrac{0.7167*0.2833}{1200}}\\\\\\ \sigma_p=\sqrt{0.000169}=0.013[/tex]
The critical z-value for a 94% confidence interval is z=1.8808.
The margin of error (MOE) can be calculated as:
[tex]MOE=z\cdot \sigma_p=1.8808 \cdot 0.013=0.0245[/tex]
Then, the lower and upper bounds of the confidence interval are:
[tex]LL=p-z \cdot \sigma_p = 0.7167-0.0245=0.6922\\\\UL=p+z \cdot \sigma_p = 0.7167+0.0245=0.7412[/tex]
The 94% confidence interval for the population proportion is (0.6922, 0.7412).
